A method is described for the detection of anthelminthic potency. The procedure does not call for exceptional technical skill, is relatively economical of drugs and living material alike, and is rapid and convenient in application. It has certain limitations such as are inherent in any in vitro method, and a special limitation in that it is not applicable to the study of drugs which act otherwise than on the neuro-muscular mechanisms of nematodes. Within these limitations it responds to compounds of known anthelminthjc efficiency and shows little or no response to compounds known to be devoid of anthelminthie value. Approximate quantitative data can be obtained with its aid, the reactions provoked by a given drug are substantially the same in different individuals, and each test provides a visible record of the influence of the drug under examination.

We do not claim that this procedure can in any sense replace experiments upon infested hosts, but must rather be followed up by such experiments when a promising degree of anthelminthie potency has been detected with its aid. We do, however, believe that it has a very real usefulness within the field to which its application is limited. As a preliminary device which allows the selection of promising compounds from large groups of new synthetic products it has already demonstrated its value in tests carried out in this laboratory on a series of about fifty new compounds prepared by Prof. Friedmann.

Some account is given in this paper of certain nematodes obtained by Prof. G. E. Gates from the coelomic cavities of various species of earthworms from South India, Assam and Singapore. The material was kindly submitted to the writer by Prof. Gates in 1936, 1937 and 1939. Of the forms included in it several were represented by specimens insufficient or unsatisfactory for adequate description, and it has seemed advisable to deal only with those species of which a reasonably full account can be given. Of these there are seven, all of which are thought to be new. Four of them can be assigned to a known genus, Synoecnema de Magalhães, 1905; the other three probably represent as many new genera.

1. Three new species of dermanyssid mites of the subfamily Entonyssinae are described. These are: Entonyssus heterodontos n.sp. from Heterodon contortrix contortrix, Ophiopneumicola elaphes n.sp. from Elaphe obsolete, obsoleta, Ophiopneumicola natricis n.sp. from Natrix sipedon pictiventris.

2. Keys for the identification of male and female mites of the Entonyssinae are given.

3. 141 snakes, representing thirty-five species, were examined for lung mites. Thirteen individuals, representing eight species, were found to be infested.

4. Two species incertae sedis, one from Pituophis sayi, the other from Coluber constrictor flaviventris, are discussed.

5. Problems of classification and distribution of this group of parasites are discussed.

1. This memoir amplifies my accounts of Endolimax nana published in 1919 and 1933. The complete life-history, as observable in cultures, is now described—special attention being devoted to the nuclear structure at all stages.

2. Additional information is also given about methods of cultivation, viability of the cysts in vitro, the ‘nucleal reaction’, natural parasites (Sphaerita, etc.), and other details.

3. The life-history has been found to comprise trophic, precystic, cystic, and metacystic stages, comparable with those described in Entamoeba histolytica (1928) and E. coli (1938).

4. The trophic amoeba is redescribed, with special reference to the polymorphism of its karyosome.

5. Division of the trophic amoeba (by binary fission) has been studied, and the mitosis of its nucleus is now first described in detail. It is characterized by the formation of an intranuclear spindle, with well-developed centrioles and centrodesmus. The granular chromosomes are 10 in number, and arranged in a ring on the equatorial plate.

6. Precystic amoebae are smaller than trophic forms —the reduction in size being effected during the last two divisions before encystation.

7. The cyst is formed by a precystic amoeba in the usual way. Inside the cyst, the nucleus undergoes two successive mitotic divisions similar to those seen in trophic forms. The ripe cyst is therefore 4-micleate, though supernucleate specimens—which are viable— occur occasionally. Glycogen is normally present in young (1- and 2-nucleate) cysts, but not in those which are mature.

8. The process of excystation is described for the first time, and closely resembles that seen in E. histolytica. The entire protoplasmic contents emerge as a single 4-nucleate amoeba through a minute pore in the cyst wall.

9. Metacystic development—not previously studied —consists in simple division, by successive cytoplasmic bipartitions without division of the nuclei, into 4 uninucleate amoebulae. These grow into trophic amoebae once more.

10. The whole life-history is thus asexual, with no gametes, conjugation, or autogamy, at any stage.

A virus disease of Atropa belladonna caused by a new virus is described. The virus is sap-transmissible to tobacco and other solanaceous plants and gives good local lesions on Nicotiana glutinosa and Phaseolus vulgaris. It occurs in fairly high concentration in the plant, it withstands ageing in extracted sap for 6–11 days, and is inactivated at a temperature between 75 and 80° C.