1. Attempts were made to cultivate in sterile artificial media the sterilised first parasitic larva of intestinal nematodes of sheep. These larvae were obtained by artificial production of the second ecdysis in 1 in 20 dilutions of Milton hypochlorite in distilled water.

2. Over 1,500 larvae were thus isolated, usually in hanging drops, in more than 200 different sterile media, containing ingredients likely to be present in the normal environment of these larvae inside their hosts.

3. None of the larvae showed any growth. Most formed the next sheath and were ready for the third ecdysis, but only 10 larvae actually performed this. The parasitic third larva thus liberated always emerged by a rent at the side of the eosophageal region of the sheath, and never by detachment of a cap like that characteristic of the second ecdysis. In every instance the parasitic third larva died immediately after the third ecdysis, which set it free. Two of these 10 larvae underwent the second and third ecdyses simultaneously.

4. The methods used by the writer (1933b) to induce artificially the second ecdysis always failed to produce the third ecdysis. No method of producing this at will was found.

5. The longest time any first parasitic larva lived was 41 days. Few of them lived, however, less than 8–10 days. A life of 18–30 days was more usual before visible signs of physiological abnormality appeared, such as the gradual vacuolation and emptying of the intestinal cells which usually preceded their death.

6. Those which were ready with a loose sheath for the third ecdysis, showed, as infective larvae also do, remarkable powers of resistance to changes produced in them by osmotic factors.

7. None of the larvae showed any particular reaction to blood, mucosa of the stomach or duodenum, nor, indeed, to any of the ferments or tissues these larvae encounter in their hosts. They seemed to be as indifferent in this respect as the sheathed infective larvae are.

8. A comparative physiological study of the sheathed infective and the exsheathed first parasitic phases of the second larva would verify, and perhaps modify, our knowledge of the functions of the so-called protective sheath of the infective larva.

Steiner (1931) published a brief note on the occurrence of disease in a yam tuber, from Jamaica, with which there were associated large numbers of a species of nematode which he placed in the genus Hoplolaimus. Steiner and LeHew (1933) published a description of the nematode parasite obtained from this yam and gave it the name Hoplolaimus bradys. At a later date Steiner and Buhrer (1934) recorded the same parasite from a yam coming from Porto Rico.

1. The preparation of a cercarial antigen from infected livers of Oncomelania hupensis the intermediate host of Schistosoma japonicum in China is described.

2. The sera of 49 human beings and five dogs have been investigated for the Schistosome complement fixation reaction, using as antigens Bilharzial cercarial antigen, and an alcoholic extract of the livers of Oncomelania hupensis infected with cercariae of S. japonicum.

3. Thirty-seven of the 49 sera examined were from cases of Schistosomiasis, and of these 24 gave a positive complement fixation reaction, and 2 others a weak reaction.

4. Of the five dogs examined three were infected with Schistosoma japonicum. These gave positive reactions.

5. In 24 cases both antigens were used, and the results obtained were almost identical.

6. The Bilharzial antigen was used in 33 cases including 25 cases of Schistosomiasis, of which 19 gave a positive reaction.

7. In 40 cases the Oncomelania antigen was used. This series included 32 cases of Schistosomiasis of which 23 gave a positive reaction and 3 a weak positive reaction.

8. Negative results were obtained with 50 strongly positive Wasserman sera, and with 2 cases of infection with Fasciolopsis buski, and two cases of Clonorchis sinensis. Ascaris and hookworm infestations also gave negative results.

The study of populations of animals has received the attention of a large number of workers. Of these, however, but a few have been interested in the problem in its application to parasitic nematodes and in this field there is consequently a limited literature. Particularly is this so when the parasitic nematodes of sheep are considered, the incentive for study of which, in most cases, has been the pressing need for their destruction. This desire has been fulfilled to a greater or lesser degree, but at the expense of researches which would have contributed to a more fundamental knowledge of the ecological relationships of parasitic worms in general.

In August 1933, Mr. W. Usher, Assistant Agricultural Organiser for Shropshire, called the writer's attention to a partial failure of spring oats at Montford Bridge, Shrewsbury. The Advisors in Agricultural Chemistry and Mycology for the West Midland Province had previously inspected the crop and had failed to find evidence of any manurial deficiency or fungal attack likely to be responsible for the failure. A careful examination of the roots of unthrifty plants by the writer, however, showed that they were heavily attacked by Heterodera schachtii in all stages of development. Further observations revealed that although the cysts of this eelworm were present on the oats over the whole field, very little disease was apparent on the plants except on those growing in certain “sick” areas. The plants in these affected patches were very much stunted, with small ears and shrivelled grain, the foliage was pale in colour and the lower leaves in most cases dead, the roots were excessively branched and rather heavily infested with H. schachtii. It would appear that the infection by the eelworm in the present instance is one of long-standing since cereal crops, particularly oats, had been almost a complete failure for some years in these “sick” areas. It is also significant that the infested areas which were of varying size had in recent years, according to the farmer, greatly increased in extent and that with each successive oat crop new affected patches had made their appearance. In view of this apparent old-standing infection, a special search was made for the presence of H. schachtii on cereal crops in other fields in the neighbourhood. It soon became evident in the course of this preliminary search that H. schachtii was already well established on several farms in the district and that besides oats, wheat and barley were also subject to infestation. The investigation was continued the following year when all cases of failing cereal and other cultivated crops reported in Shropshire were examined. In addition, a thorough examination was also made of the roots of apparently healthy looking crops in the immediate neighbourhood of those failing ones that were found infested with H. schachtii. Later in this paper the general field observations made during this investigation are described, together with an account of some cultural experiments that were carried out with a view of determining whether the race of H. schachtii found parasitic on cereals in Shropshire is capable of attacking other plant species of economic importance and whether this race is distinct from those commonly found in the County on potatoes and peas, respectively.