1. The proportion of stained spermatozoa in a ram semen-nigrosin-eosin mixture has been found to increase with the time of exposure to the stain. Five minutes is considered to be a suitable interval for practical use.

2. The value obtained for the proportion of dead cells can be considerably affected by the selection of fields that are easy to count; fields should be chosen at random.

3. The variation between, counts on the same smear is much larger than that expected for binomial proportions. This may be due partly to the ‘clumping’ of the dead spermatozoa and partly to the difficulties of interpretation caused by the presence of many partially stained cells.

4. A significant difference was found between the estimates of the proportion dead obtained by the two experimental workers; this is thought to be due to a difference of interpretation of ‘stained’ and ‘unstained’.

5. Tables are given by which to determine the approximate accuracy of counts made on a range of numbers of spermatozoa, smears and subsamples, separate tables being necessary for ram, boar and bull semen.

Experiments on the milking qualities of New Zealand Romney ewes, maintained at liberal standards of grazing and at different planes of nutrition under stall-feeding conditions, were described in four earlier papers published in this Journal (Barnicoat, Logan & Grant, 1949).

In the meantime several other original papers in this field have appeared: Coop (1950) studied the effect of certain factors including milk intake on the growth and development of lambs of various breeds of sheep in the South Island of New Zealand; Barnicoat (1952) discussed some practical applications of the work; Owen (1953), employing a modified technique for measuring milk yields of Welsh hill ewes, found that the correlations between lamb gains and estimated milk yields were of a similar order to those established elsewhere under easier conditions of farming; Thomson & Thomson (1953) carried out experiments with Cheviot ewes fed indoors, and their results support the viewpoint that adequate nutrition in the final stages of pregnancy is of paramount importance; and Gill & Thomson (1953) discussed the significance of milk yield of ewes under farming conditions in Great Britain which contrast widely with conditions pertaining to the district in which the experiments described in this series of papers were conducted.

The influence of the maternal environment on the size of lambs from birth to 8 months has been studied by reciprocally crossing the large Border Leicester and the small Welsh Mountain breeds of sheep and by transferring fertilized eggs between ewes of these breeds.

Ewes which lambed later in the spring gained more weight during the last 6 weeks of pregnancy than did the earlier-lambing ewes. The birth weight of the lambs was not, however, affected by either the date of lambing or the ewes' gain in weight during the last six weeks of pregnancy.

Significant breed differences in gestation length were recorded; these were 144·7 days for the Border Leicester and 147·1 days for the Welsh Mountain. Border Leicester ewes carrying pure-bred Welsh lambs had an average gestation of 149·6 days, while Welsh Mountain ewes carrying pure-bred Border Leicester lambs had an average gestation of 146·0 days. From the births of ‘transferred’ lambs, it appeared that the genetically smaller lamb was a cause of a longer gestation period. On the other hand, within groups, both live weight and length of ‘cannon bone’ of the lambs at birth increased when the gestation period was longer.

The maternal environment affected foetal growth when the genotype for size of the foetus was different from that of the mother. The mean live weight and ‘cannon-bone’ length of cross-bred lambs born to Border Leicester ewes were 1·08 lb. and 0·37 cm. greater at birth than those of cross-bred lambs born to Welsh ewes. Comparable figures for the maternal influence from the results of transferring eggs from one breed to the other were 1·96 lb. and 0·33 cm. On the other hand, within breeds, there was no effect on the size of the lambs at birth of variations in the size of the ewes. The length of the ‘cannon bone’, which grows relatively rapidly during the early stages of growth (an early-maturing part of the body), was less influenced by the maternal environment than the late-maturing live weight.

Mature ewes produced larger lambs at birth than young ewes. The mean differences at birth in weights and in lengths of ‘cannon bone’ of the lambs born to young and mature ewes were 1·38 lb. and 0·31 cm. respectively.

From these and other experiments, the conclusions were drawn that: (i) the maternal influence on the size of young at birth is greater, in the larger species which have longer gestation periods, than the effect of the genotype of the young; (ii) the maternal organism competes with the foetus for nutrients, thus limiting the size of the young at birth; and (iii) the maternal organism may also influence pre-natal foetal growth by means of some internal secretion or metabolic substance.

The amount of milk consumed by the lambs had a marked effect on their live weight gains during the first half but not during the second half of lactation. Variations in milk consumption by the lambs did not affect the growth in length of their ‘cannon bones’. The influence of the post-natal maternal environment is largely exerted through the milk yield of the ewe and causes of variation in this milk yield were reflected in the post-natal maternal influence estimated in these experiments.

The total milk yield of ewes was affected by their date of lambing, that of late-lambing ewes being less than the yields of ewes which lambed earlier in the season.

1. Carcasses of twenty-one fat cattle (from six cows, ten steers and five heifers, aged from 12 months to 12 years and representing seven breeds) have been dissected into nine joints, and the fatty and muscular tissue from each joint dissected and analysed for fat. The iodine number of each sample of fat has been determined.

2. The fat in fatty tissues ranged from 28·3 to 96·7%, and in muscular tissues from 1·3 to 14·2%. Iodine numbers of fat from fatty tissues ranged from 34·0 to 69·0 and those of fat from muscular tissues from 45·9 to 73·2.

3. By an analysis of covariance it has been possible to reduce these data to two families of regression lines—those for fatty tissue and those for muscular tissue.

4. The equations for fatty tissue have the following generalized form:

I.N. = AFT + CFT + JFT + b1F/FT,

where AFT = 55·6 ± 1·7 and is a general constant,

CFT is a series of constants for the various carcasses and ranges from +12·6 to −6·7,

JFT is a series of constants for the various joints and ranges from +6·6 to −10·3,

b1 is a general constant with the value −0·052(± 0·025),

F/FT is the percentage of fat in any given sample of fatty tissue, and I.N. is its iodine number.

5. A similar set of equations has been deduced for muscular tissue. Here, however, the relation between iodine number and percentage of fat is a rectangular hyperbola. Consequently, the inverse (Z) of the percentage of fat (in order to get a straight-line relationship) has been used.

The results of over 400 field experiments testing different kinds of phosphate fertilizers are summarized and are discussed with special reference to the reactions of the soils used. The classifications were:‘very acid’ soils—pH below 5·5, ‘acid soils’— pH 5·6 to 6·5, neutral soils—pH over 6·5. All comparisons are made in terms of fertilizers supplying the same amounts of total phosphorus.

In war-time experiments Gafsa and Morocco rock phosphates were about two-thirds as efficient as superphosphate for swedes and turnips grown on very acid soils. In 1951–3 experiments on very acid and acid soils Gafsa phosphate was practically equivalent to superphosphate for swedes, but for potatoes it was as effective as only one-third as much phosphorus supplied as superphosphate; on neutral soils Gafsa phosphate was useless. For establishing grassland on acid soils Gafsa and Morocco phosphate were equivalent to about onethird as much phosphorus supplied as high-soluble basic slag. Rock phosphates were somewhat more effective for promoting growth of established grassland but they remained inferior to high-soluble basic slags and to superphosphate. Curacao rock phosphate was roughly equivalent to Gafsa phosphate for swedes and grass. Florida pebble phosphate was much less effective and was judged unsuitable for direct application. Mixtures of rock phosphate with superphosphate were not more efficient than equivalent amounts of the separate components used correctly.

Silicophosphate was practically as effective as superphosphate for swedes grown on very acid and acid soils; it was less efficient on neutral soils. For potatoes silicophosphate was nearly as effective as superphosphate on very acid soils; it was much less efficient on acid and neutral soils. Silicophosphate was roughly equivalent to high-soluble basic slag for grassland.

Mixtures of superphosphate with lime, serpentine, and low-grade basic slag were prepared, most of the water-soluble phosphorus being converted to insoluble forms. In experiments on swedes and potatoes these basic superphosphates were not superior to untreated superphosphate. For establishing grassland on very acid soils, the mixtures were slightly superior to ordinary superphosphate.

Dicalcium phosphate was practically equivalent to superphosphate for swedes on all groups of soils. For potatoes dicalcium phosphate was more efficient than superphosphate on very acid soils, on less acid and neutral soils it was inferior to superphosphate.

1. The reaction of spring and winter types of field beans and of Windsor broad beans to artificial vernalization treatments and to successional field sowing has been studied.

2. The broad bean type came into flower earlier and at a lower node on the stem than any of the field bean types, and this was not affected by either vernalization treatments or successional sowing.

3. The field bean types flowered at a low node when sown in winter, but in summer sowings the level of the first flowering node was much higher; the response of the winter types was more extreme than that of the spring types.

4. In the summer sowings vernalized plants came into flower earlier and at a lower node than unvernalized, but in the winter sowings both vernalized and unvernalized material flowered at an equally low node.

5. A convention for naming the different stems contributing to the yield was evolved, and using this it was shown that the date of sowing affected the stems produced.

6. The survival of plants in the field was not found to be affected by vernalization previous to sowing.

1. The effect of three factors (nitrogen level, time of nitrogen application and weed control) and their interactions on three different plant densities of winter wheat have been measured. Data concerning the growth, development and yield have been examined.

2. Plant populations of 104,000, 155,000 and 281,000 per acre produced on the average of all treatments 21·3, 22·4 and 23·2 cwt. grain per acre, respectively.

3. An increase in nitrogen fertilizer to the 2 cwt. sulphate of ammonia per acre level increased the grain yield of all populations. This response followed an increase in the number of tillers and an increase in the percentage of tillers producing ears. There was no significant interaction between nitrogen level and plant density. The nitrogen content of the grain increased with nitrogen level.

4. Time of nitrogen application did not affect the grain yield, although it did cause considerable differences in the growth and development of the plants. There was no significant interaction betweentime of application and plant density. The late application of nitrogen produced a lower yield of straw and a higher nitrogen content in the grain.

5. Weed control increased the grain yield of all plant populations, this increase following an increase in the number of ears per plant. There was a significant interaction between weed control and plant density. Weed control raised the yield of the low plant population by 3·9 cwt. per acre compared with 0·9 and 2·0 cwt. for the medium and high populations. Weed control also increased the nitrogen content of the grain.

6. The only other interaction concerning grain yield which was significant was that of weed control with time of nitrogen application. Weed control increased the yield of the early and late applications but inexplicably reduced the yield of the intermediate date.

7. It is concluded (a) that the experiment provided no evidence that the yield of a thin stand of winter wheat can be increased further by altering normal nitrogen fertilizer application or by altering the time of application of the fertilizer; (b) that for good results weed control is essential where the plant population is low.

Often the ultimate measure of performance in a field experiment is the product of a gross weight and a factor relating to quality, as when yield of dry matter is determined from gross yield and percentage dry matter. Since the factor is usually much less variable than the gross yield, yet relatively troublesome and expensive to determine, the practice of making independent estimates of it in every experiment involves diversion of an appreciable part of the total expenditure to a measurement whose inaccuracy will affect only slightly the final experimental error.

Proposals are made for determining the quality factor on only a fraction of all the experiments of one series and applying the averages to the gross yields of others in the same series; formulae and tables relating to the most economic ratio of incompletely to completely recorded experiments are presented.