Field observations made in 1935 on a potato crop growing on what was thought to be potato sick land in Bedfordshire seemed to indicate that eelworm damage due to Heterodera schachtii was less pronounced where maize had been the previous crop than in other cases. As particulars of the history of this piece of ground were not available, detailed observations were not made, but it was decided that it might be valuable to carry out experiments with maize to determine whether this plant had any effect on eelworm cysts. Other members of the natural order Gramineae have been shown by Triffitt to stimulate the larvae of H. schachtii to hatch from the cysts, and it was thought that maize might have a similar effect.

It is a well known fact that Heterodera schachtii in the brown cyst stage can survive in soil for several years in the absence of host plants. Fuchs found living contents in five-year old cysts of the beet strain of this nematode, while eight-year old cysts of the potato strain have been found by the writer still to be infective to the host plant. Thus, the starving out of this parasite by withholding susceptible crops would appear to be impracticable.

Potato tubers infected with Heterodera marioni having been received at this Institute, it was decided to attempt to infect a small field plot with this eelworm for experimental purposes. The tubers were planted in the plot but the infection never became established. This was thought to be due to the heavy nature of the soil, since H. marioni has been recorded as a field parasite in Britain (Triffitt, 1931), and it is therefore unlikely that climatic conditions were the cause of its failure to become established in this instance. In order to verify this, and to find out how long this parasite can survive in soil in the absence of a host, the following experiment was carried out.

Although the “potato-sickness” associated with the nematode Heterodera schachtii has been the subject of a good deal of investigation in Britain during the past twelve years, the only practical method of control so far devised is the adoption of a well-planned crop rotation in which potatoes are omitted for several years. The limitation of a general application of this method to the thousands of acres of land infected with this eelworm disease but otherwise admirably suited for the growing of potatoes has led to insistent demands for further study into chemical treatment of affected soil. In the present investigation, comparative control trials of soil treatment by certain chemical substances were carried out on land known to be thoroughly “potato-sick” and the last potato crop grown in it had been a failure. Most of the experimental treatments had already shown in other field experiments some measure of protection from “potato-sickness,” at least, judging by the healthier appearance of the foliage and increase in yield of crop. Although the results of previous experience indicated that there was a positive association between application of these various soil dressings and intensity of disease, it was felt that a more accurate computation of the latter, by measuring the eelworm cyst content of the soil, was desirable before any definite conclusion might be drawn.

The species Bucephalopsis karvei n. sp. has been described in detail and separated from the allied species. A survey of the work on Bucephalidæ has been given and the species B. magnum, B. confusus and B. minimus have been considered to be synonyms of B. garui. A key to the existing valid species of Bucephalopsis has been given.

The genus Catoptroides has been merged into the synonymy of Phyllodistomum and arguments for so doing have been advanced. Revised diagnosis of Phyllodistomum has been given.

Phyllodistomum shandrai n. sp. has been described and separated from the allied species. P. sp. has been briefly described. Key to the species of Phyllodistomum has been given.

Paramphistomum maplestoni n. sp. and P. cuonum n. sp., have been described and separated from the allied species P. orthocœlium. A few observations on P. sp. from a wild cat and Diplodiscus amphichrus from Rana tigrina have been recorded. Paramphistomum cervi, P. sp., Cotylophoron orientalis and Gastrothylax crumenifer have been recorded from neelgai, hog deer and sable antelope respectively.

Helostomatis sakrei n. sp. has been described and separated from H. helostomatis. A revised diagnosis of Helostomatis has been given.

Neocladorchis poonaensis n.g., n. sp. has been described. The new genus Neocladorchis has been defined and separated from the allied genera.

In a memoir on human and animal schistosomiasis (1934c), I reported the presence of bovine schistosomes for the first time in the Belgian Congo (Elisabethville). I also expressed the opinion that the bovine schistosomiasis in Katanga was of Rhodesian origin. It came from that same region from which Veglia & Leroux in 1929 described a new schistosome of Bovidae and Ovidae under the name Schislosoma mattheei, a species which has since given rise to some controversy. The material I brought back from Elisabethville readily lent itself to a morphological study of the two African bovine schistosomes.