The object of this experiment was, in the first place, to see whether, with cotton experiments, there was an advantage in planting a larger number of seeds per hill than the customary number of three; and, in the second place, to see the effect of the interaction of time of thinning with varying numbers of seeds per hill.

In cotton breeding work, where trials of new strains have to be carried out as soon as sufficient seed is available, it is important to conserve seed in all possible ways. At the same time it is necessary to plant sufficient seed to give a full and even stand for all strains.

In experiments carried out in 1936–7 and 1937–8 stand counts, made soon after germination, showed the advantage of the higher seed rates in obtaining a quick and full stand. Later counts and final counts at harvest showed a considerable evening up, although the two-seed treatment proved unreliable, giving the lowest stand in both seasons.

Plant height and weight records, made during both seasons, showed that plants from the larger hills were drawn up much more rapidly than plants from the smaller hills. This rapid elongation in stem height proved, from weight figures, to be at the expense of lateral development, weak and leggy plants being produced in these hills. The ten-seed treatment showed up particularly badly in this respect, the yield figures showing that the plants never recovered from this early deleterious effect.

The six-seed treatment, whilst giving a quick and excellent stand suffered to a certain extent from the same defects as the ten-seed treatment. If thinned early they tended to fill out and become more comparable with plants from the three-seed treatment, but when thinning was delayed they never caught up and final yield suffered adversely.

The design and field technique of two large scale experiments, laid down to investigate the problems of sampling and “propinquity”, are described in detail. These experiments were designed so that the plant number, stem number, ear number, straw weight and grain weight for 7200 lengths of 6 in. of drill row, together with the position of each observation, might be obtained.

The lowest sampling error, expressed as a percentage of the mean, is obtained by using the smallest sampling unit, but the large number of sampling units of this size that would have to be taken make it impracticable. The optimum sampling unit consists of 6 ft. of drill row, taken as 3 ft. of two adjacent rows. The size of the sampling unit is of greater importance than the shape in determining its accuracy, and little s lost by using sampling units of 18 in. of five adjacent rows.

The nature of the observation affects the degree of sampling. In the experiments examined the plant number, stem number and ear number require very similar sampling, but grain weight requires a sample which is about twice as large as that required by the other observations.

The percentage of the plot that must be taken as a sample (the sampling percentage) to obtain any given accuracy is related to the size of plot: the larger the plot, the lower the sampling percentage necessary. To obtain an error of 5% of the mean the sampling percentage for grain weight is approximately 5% in 1/20 acre plots, 15% in 1/100 acre plots and 43% in 1/600 acre plots if the plots are not subdivided. These percentages are similar to those calculated from various randomized block experiments in Cambridge.

The majority of methods for determining carotene involve a preliminary determination of total carotenoids, followed by a phase separation of the two pigments. This phase separation considerably limits the usefulness of such methods, and in order to dispense with it a direct extraction of carotene is necessary. For this purpose petroleum ether may be used in the presence of alcohol.

The use of hot alcoholic potash for the disintegration of leaf material and separation of chlorophyll leads to a very undesirable precipitate which hinders subsequent extraction. Two alternative methods are available, which overcome this difficulty, viz. (1) extraction with hot alcohol, followed by treatment of the extract with potash, and (2) saponification with hot aqueous potash, followed by filtration and extraction of the grass residue with alcohol. The second of these methods has been adopted, being of greater general utility and capable of producing complete cellular breakdown, which is essential for efficient extraction. Details of this extraction process have been described.

A comparison of the results obtained, with those from two other methods, has been made by a colorimetric determination of the extracted pigment. The variance and standard error have been shown to be smaller than those for the other two methods, and it has been concluded that the results obtained are reproducible with considerable accuracy.

1. A study was made of nitrogen-fixation by Azotobacter chroococcum alone in a medium containing dextrose (which it can utilize) and in mixture with a coliform organism on a medium containing no carbohydrate except starch, which Azotobacter cannot utilize unless it be hydrolysed by the coliform organism or some other agency.

2. The amount of nitrogen fixed in the mixed cultures was found to be maximal at two temperatures, and a discussion is given of the causes thought to be operative in producing the double maximum.

Analysing Hammond's data on the growth of limbs in the sheep, Huxley (1932) found a post-natal simple negative heterogony, or allometry, as in the latest terminology (Teissier, 1937), of the whole limb relative to the body. As lambs, and the young of most other grazing mammals, are born with relatively long limbs enabling them to follow their dams (Hammond, 1932), the same author pointed out that the leg must have exhibited positive allometry during foetal development.

Having possession of a sufficient body of measurements on the skeletal development of female calves of the Chianina breed, a very tall beef and draft breed of cattle of Central Italy, I investigated the course of growth of height at withers relative to the growth of the length of the trunk (from shoulder to ischium). The growth of height at withers can be considered as a sufficiently reliable measure of the growth of forelimb length owing to the fact that the two principal angles in the limb (scapula-humerus and humerus-radius) do not change very much with age (Engeler, 1935).

It was found that the growth of forelimb length in this breed of cattle exhibits a simple negative allometry relative to the growth of trunk length. This simple allometry, with growth constant about 0·78, holds from birth until over the age of 3 years, that is, throughout practically the whole post-natal growth.

Lack of data after this age leaves open to further research the course in the ultimate period of development.

I thought it would be of some interest to compare various breeds of cattle differing rather widely in the absolute values, as well as in the proportions of height at withers and trunk length at birth and in later life.

Some years ago my colleague, Mr E. T. Halnan, suggested the construction of the present instrument for the purpose of determining figures for domestic fowls corresponding to those of Kellner for ruminants.

Owing to the activity of the fowl, it is essential that an instrument for this purpose should be capable of recording accurately a heat output which may be varying with some rapidity.

From this point of view the advantages of the indirect method were considered but were eventually rejected for the following reasons: (a) the advantage accruing from our greater experience of the direct method in this laboratory, (b) the work of Adams & Poulton (1933, 1934, 1935) calling in question the fundamental bases of the indirect method, and (c) the very variable R.Q.'S obtained in earlier work by numerous investigators working with birds.

That the decision was wise soon became apparent when work on birds was begun. It is certain that no ordinary apparatus of that kind could possibly take account of the variations caused by the constant changes in activity.

The principle of a “compensatory” or “balanced” calorimeter more or less as developed by Noyons (1927), Benedict (1927) and Heyster (1933), was selected as the most likely to give promptness in registration, and this choice has been amply justified in the result. Such instruments can be very lightly constructed, although where living animals are concerned, since their movements cannot be controlled, as can those of a human being, a greater margin of strength has to be provided, which naturally increases the heat capacity and lag and reduces sensitivity to small changes in heat evolution.

The influence of three feeding treatments of differing protein content on growth and carcass quality in bacon pigs has been investigated by the individual-feeding and group-feeding techniques. The protein supplement, which was used in conjunction with barley meal, weatings and a small allowance of lucerne meal, was composed of a mixture of ex. soya-bean meal, dried separated milk and feeding blood meal. Expressing, on the nitrogen basis, the amount of protein food in terms of its equivalent of white fish meal, the standard-protein treatment B supplied the equivalent of 9% of fish meal up to 90 lb. live weight, 7·6% from 90 to 150 lb. live weight and 3·8% from 150 to 200 lb. live weight. The corresponding figures for the low-protein treatment A were 4·5, 3·8 and 1·9%, and for the high-protein treatment C, 18, 15·2 and 7·6%.

Considering the period of feeding up to 200 lb. live weight as a whole, it was found that differences of feeding treatment gave rise to no significant differences in respect of mean rate of live-weight increase and efficiency of food conversion (see Table VI). Only in the earliest stage of the feeding period did the pigs on the low-protein treatment A show a slightly, though significantly, lower rate of live-weight increase and poorer efficiency of food conversion than the pigs on treatments B and C, but such differences had ceased to be manifested by the time the pigs had arrived at 60 lb. live weight, and the slight initial disadvantage experienced by the low-protein pigs was wiped out during the later stages of the feeding period.

The effect of rainfall, sowing date and yield on the percentage of nitrogen in the barley grain of certain representative plots on Hoosfield is studied.

All these factors are shown to have marked effects. The farmyard manure plot differs from the others, both in mean percentage and in the effects of rainfall and yield.

Changes in variety appear to have had little apparent influence, but there is a progressive decrease in the percentage of nitrogen which cannot be accounted for by changes in any of the above factors, and which may well be due to varietal improvement

Comparison is made with the results of the similar study on the permanent barley plots at Woburn.

An investigation into the effects of lime on five acid soils in north-east Scotland has been continued during the second and third years after the application of lime and also extended to two other centres.

On four of the original soils the full effect of the lime on the surface soil has been largely maintained up to the end of the third year. The fifth, a soil of low base-exchange capacity, shows a considerable loss of lime by the end of the second year.

The lime leached from the top nine inches of soil appears to be retained to only a slight extent in the second nine inches. This was particularly noticeable on a soil of low base-exchange capacity, where, during the two years after liming, the percentage saturation of the subsurface soil showed an increase from 64 to 67%, and the surface soil a decrease from 92 to 74%.

The existence of a low liming factor (1·5), previously found to hold for a geologically basic soil, has been verified and found to apply also to a soil derived from slate.

A fundamental property of the soils with a low liming factor is the high content of inorganic and organic fine material. Secondary characteristics that distinguish these soils from the others are the relatively high values for hygroscopicity and heat of wetting.

1. The quality status of Danish and English Wiltshire bacon sides representative of the highest grades produced at the present time has been investigated by the use of carcass measurements. The data resulting provide “standards” for practical guidance in stock improvement work on bacon pigs, and for the evaluation of experimental treatments involving bacon quality.

2. The variability of the respective characters has been compared by means of the coefficient of variation of each. The results indicate that while selection on a basis of “external characters” and of such internal characters, as are readily measurable, leads to marked uniformity in respect of these characters, it does not necessarily involve similar uniformity in respect of important “internal characters” which are not taken into account in either stock selection or commercial grading practices.

3. External characters thus do not provide a reliable indication of the internal quality status of the bacon pig, and since it is the latter which largely governs the cutting value of the side, concentration upon addition to the former is desirable if still further improvement in the quality of the bacon pig is desired.

4. Variability appears to be affected also by the rate of development of the character concerned; late developing characters in general tend to be more variable than early.

5. The intimate association between nutrition and the rate of development of the various parts and tissues of the pig provides a method of control in addition to that of selection.

1. In mares which had a follicle of a sufficient size in the ovaries, in most cases the intravenous injection of 1000 mouse units or over of pregnancy urine extract caused ovulation at any time in the oestrous cycle.

2. In those mares which were in oestrus at the time of injection, ovulation occurred 22–30 hr. after injection, and the length of oestrus was reduced from 7 and 9 days to 3 days.

3. In those mares which were not in oestrus when injected ovulation occurred 30–60 hr. after injection without the appearance of any symptoms of oestrus.

4. Normal ovulation occurred after these injections, and in one case the ovum was recovered from the uterine end of the Fallopian tube about 95 hr. after ovulation, and 138 hr. after injection.

1. The removal of the foetus between the 51st and 105th day of pregnancy in the mare, did not have any detrimental effect in seven Welsh pony mares.

2. The subsequent oestrous cycles of the mares did not appear to be influenced by the stage of pregnancy at which the foetus was removed.

Six litters of pigs farrowed, reared and fattened on a ration of barley meal, weatings, soya-bean meal, meat meal and minerals failed to thrive and in the later stages of fattening many of the pigs showed typical symptoms of vitamin A deficiency.

Six comparable litters raised under similar conditions and on the same meal mixture with ° 1 or 2% of a commercial cod-liver oil of guaranteed purity and standardized vitamin content made good progress and nearly all the pigs weaned in these litters were fattened for pork or bacon.

Estimations of liver reserves of vitamin A of the pigs receiving no cod-liver oil indicated that the liver store was exhausted soon after weaning. All pigs receiving cod-liver oil gradually increased their liver store of vitamin A. The stores rose approximately in proportion to the level fed and period of feeding. There was no evidence that the higher levels of cod-liver oil had any practical advantage over °%.

The symptoms shown by the pigs receiving no cod-liver oil included loss of appetite, cessation of growth, impairment of vision in daylight, abnormal gait, convulsive fits and nervous collapse. Pneumonia and/or inflammation of the intestines was found in all of seven pigs that died during the fattening period.

1. Two experiments have been carried out on the Cambridge University Farm to test the desirability of including late-flowering red clover in the seeds mixture in the case of a 4-year ley, and to compare grazing with cutting for hay in the first harvest year.

2. The majority of the red clover survived for the first 2 years, during which it increased the yield of dry matter very markedly; it did not lead to any reduction of yield in the last 2 years. By producing an early cover of the ground red clover checked the encroachment of weeds; although it reduced the proportion of wild white clover in the herbage in the later years, the reduction was not serious.

3. Where the young plants were well established at the time, and normal weather conditions were experienced, grazing was definitely preferable to cutting for hay during the first harvest year. Where the plants were slow in establishing themselves, and in a superlatively dry spring and summer, grazing checked the development of the sward too much, and cutting for hay gave much better results.