The nematode has been known as a serious parasite of potatoes for a number of years. The disease produced by it was first described in Germany by Kühn (1888) under the name of Wurmfäule. Shortly after this Ritzema Bos (1892) confirmed and amplified Kühn's account and carried out an experimental investigation on the disease. The present writer Goodey (1923) gave a short résumé of this earlier work and an account of the occurrence of the disease on potatoes in the Holbeach area of Lincolnshire. Buckhurst (1925) also reported the results of certain successful pot experiments in which potatoes were infected by growing in soil containing diseased tuber material. Finally, an important paper by Quanjer (1927) has appeared in which he deals with the occurrence of the disease on potatoes at Wageningen, Holland, and shows that the physiological race of worms attacking potatoes there occurs naturally on certain wild plants in the pastures and is capable of attacking a wide range of host plants both cultivated and wild. He also discusses the mode of entry of the parasite into the host and the nature of its action on the plant tissues.

For two years, from June, 1927, the writer held a Research Scholarship in Sanitary Science from the Grocers' Company, the terms of reference including a biological study of the fauna of sewage-treatment plants. Special attention was paid to the free-living nematodes since in mere quantity they form an important section of the fauna in many treatment units, and they have been much neglected as a group in comparison with the protozoa and bacteria.

Since the discovery of the plant-infesting nematode Heterodera schachtii Schmidt, 1871, many infections of this nematode occurring in different countries on a wide range of host-plants have been studied. Owing to the serious agricultural losses occasioned by this pest, efforts have been made, both in Europe and in the United States, to determine the range of plants which are susceptible to infection. Lists of plants susceptible and non-susceptible to attack have been drawn up by various workers, and these have comprised not only plants of economic importance, but also weeds which might serve as an important means of propagating the parasite. The abundance of contradictory evidence which appears in these lists is only explicable by Steiner's (1925) exposition of the hypothesis of biological or physiological strains. This work serves to emphasise the importance of crop rotation as a means of combating the parasite, more particularly when the nematode population constitutes a monophagous strain, i.e., one which has become highly specialised upon a single hostplant and has lost the power of readily attacking other species. Where a polyphagous strain occurs, the range of non-susceptible plants which can be used in the course of the rotation is greatly diminished, and, in such cases, the weeds occurring on the infected land may add an important complicating factor to the problem of eradicating the pest.

In the microscopic examination of plant-parasitic and free-living nematodes it frequently happens that certain anatomical details stand out clearly whilst others remain obscure. Later examination of further examples of the same species, perhaps from a different source or at another season of the year, may reveal some of the previously obscure details with the result that structures which up to that time had been difficult to elucidate, are now seen distinctly in relation to their surroundings.

During a visit to the island of St. Kitts, British West Indies, in 1928, I received from Dr. S. B. Jones for identification, a tapeworm which he had received from a young negress who had never left the island. The tapeworm was a specimen of Bertiella.

The material upon which this study is based was obtained from a Grey Sand-Hamster (Cricetulus griseus) which died in captivity at the experimental farm of the Institute of Agricultural Parasitology. Several examples of two species of hamster were received from Dr. Hindle on his return from China, the specimen furnishing the worms being one of these. On death a post-mortem examination of the animal was made and the cestodes removed and preserved in dilute formalin. Some weeks subsequently the parasites were examined and found to differ from the descriptions of other species of Hymenolepis encountered in hamsters and the present study was entered upon.

Reptiles form a very prominent part of the fauna of India, but very little is known about the Entozoa of this group in the country. The foundation of our knowledge of the Trematode parasites of Reptiles is laid by Rudolphi (1819), Dujardin (1845) and Diesing (1850–58), all of whom have described them under a common genus Distomum, along with the forms from other hosts. Von Linstow (1877–85), Looss (1899) and Lühe (1900–11) have considerably extended our knowledge of these forms. They have also revised the observations of the earlier workers and have split up the original genus into several genera, thereby placing the group on a more scientific and natural basis.

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