1. A technique is given for the detailed study of living cercariae in which reference is made to the value of human or horse blood serum as a mounting medium.

2. As a fixative agent for cercariae prior to staining the use of hot lacto phenol solution is recommended.

3. A description is given of three non-furcocercous cercariae obtained from Bullinus contortus in the Sudan.

That ducks are subject to infestation by sarcosporidia has long been known. It seems to have been emphasised particularly because ducks afforded one of the first-known instances of the occurrence of these puzzling protozoa in birds. Very few new records have been published until now and no adequate illustrations of the gross features of the infestation have appeared. A general review of the subject and presentation of additional cases, with illustrations, therefore seems desirable.

1. Embadomonas blattae a new species from the hind gut of Blatta orientalis is described. The flagellate measures 6–9 μ × 5–7 μ and the cysts 5–6 μ × 4–5 μ.

2. An Embadomonas from Rana temporaria, Bufo vulgaris, and Salamandra maculosa has been cultivated and described. I propose to call it E. dobelli. It differs from other known species of this flagellate in shape, and in absence of a definite karyosome. The flagella and their basal granules are duplicated first at division, and a centrodesmose is formed between one of each pair of basal granules. The cytostome disappears and new ones are reorganised after nuclear division is completed. Definite chromosomes were never seen. Double individuals and occasionally individuals with three nuclei were seen.

3. Cysts of E. dobelli were obtained in culture. They are uninucleate. A karyosome is formed; the peripheral chromatin of the nucleus stains intensely and becomes elongated. The lip of the cytostome can often be distinguished, and sometimes the glagella. These cysts are the same as those described originally by Dobell as cysts of Eutrichomastix batrachorum and Trichomonas batrachorum.

4. Cysts of Trichomonas batrachorum have never been found in faeces or in cultures.

That parasitic worms may induce bacterial invasion from the intestine has frequently been asserted in explanation of the sporadic occurrence of some bacterial and virus diseases of animals. Weinberg, in 1907, gave an extensive review of the literature dealing with inflammatory conditions of the intestine, due to bacterial invasion associated with parasitic worms. He also gave an account of some original clinical observations. He concluded that, by biting and boring into the intestinal wall, or by wounding it with hooks and suckers, the majority of helminths favour the penetration of microbes, these being carried on the exterior and in the intestine of the worms. In one case, where a fatal septicaemia was associated with the presence of a single individual Trichocephalus, the author's conclusion, that even isolated worms are very dangerous, appears to be rather strained. Records of clinical observations of this kind frequently appear in the literature, but, as a general rule, the evidence showing the agency of the worm is very slender and amounts to little more than the observation of the presence of worms in animals suffering from some bacterial disease.

Three species of furcocercariae are described. By means of direct animal experiment with secondary, intermediate and final hosts I have shown that one species develops into Tetracotyle typica Dies., the larva of Strigea tarda Steenstrup, and a connected detailed account of this life cycle is here given. Of the two other species, both of which are new, I have been able to trace the development of one into Tetracotyle n.sp. in Planorbis crista L., and P. albus Müll. Feeding experiments with this new Tetracotyle using ducklings as final hosts failed, however, to produce the corresponding adult.

Effect of the parasite on the host. The usual results of helminth infection of this nature are observable, namely, marked disruption of liver tissue and in many cases complete parasitic castration of the molluscs infected.

Double infection. In the course of my investigations on larval Trematodes I have met with one example of double infection with sporocysts, viz. Cercaria F.1 and F.2, within one and the same individual of Planorbis albus Müll. This condition was found only on one occasion, Cercaria F.1 being in predominance. Instances of double infection have been recorded by Faust (1971) and Sewell (1922), and from this country by Hesse (1923) and Brown (1926). The condition, however does not appear to be a common one.

In the Final Report of the League of Nations International Commission on Sleeping Sickness (1928) certain tentative conclusions were expressed about the behaviour of T. gambiense, recently isolated from man, in the blood of monkeys and of certain domestic ruminants. These conclusions, which were intended primarily to serve as a basis for further researches, were set forth in the Summary of Part I of that Report, and read as follows:

1. The red-cell adhesion phenomenon in trypanosomiasis of man and other animals, first described by Duke and Wallace (1930) and shown by these authors to be due to the presence in the blood of the infected animal of a sub-stance (adhesin) which appears during the course of an infection, has been investigated further. Several strains of T. rhodesiense and T. gambiense have been used for this study.

2. Red-cell adhesion of this nature has been obtained with the red blood cells of primates only, thus confirming the earlier finding.

3. No relationship appears to exist between red-cell adhesion and isohaemagglutination, or other types of haemagglutination. The removal, by absorption, of the α and β isohaemagglutinins from a human adhesin serum of blood group O, or the removal from a monkey adhesin serum of agglutinins for baboon, rabbit and guinea-pig red cells does not lead to the removal of the adhesin.

4. Centrifuging, per se, does not destroy to any appreciable extent the power of trypanosomes to adhere to red cells.

5. Trypanosomes which have been freed from plasma by centrifuging and subsequent washing with citrate-Ringer-glucose solution give good adhesion with human or monkey red cells when a fresh adhesin serum or plasma is used. Little or no adhesion is obtained with these washed trypanosomes however, if the adhesin serum is very old or if it has been previously filtered through a Berkefeld filter candle or if the adhesin serum or plasma has been heated at 56° C. for 30 minutes.

6. From this and other evidence the conclusion is reached that in addition to the red cells, trypanosomes and the adhesin some other factor (designated the “X” factor) is necessary for red-cell adhesion.

7. This “X” factor is present in the serum or plasma of humans, monkeys, baboons, rabbits and guinea-pigs and has properties similar to those of complement. It is removed, as is most of the haemolytic complement, when the serum is filtered through a Berkefeld filter, it is destroyed by heating at 56° C. for 30 minutes, and, like haemolytic complement, it is inactivated when the serum is subjected to the action of dilute ammonia for about 1½ hours. Filtration, heating at 56° C. for 30 minutes and dilute ammonia appear to have no significant destructive action on the adhesin.

8. The requirements for this red-cell adhesion phenomenon are (a) the red cells of a primate, (b) an adhesin, which is probably an antibody-like sub-stance produced during infection with trypanosomes, (c) trypanosomes of a strain related to that which gave rise to the formation of the adhesin, and (d) a complement-like component (“X” factor) present in the plasma and serum of most, if not all, normal animals.

1. Studies were made on the morphology, with special emphasis on the taxonomic characters, of 220 mature male and female Ascaridia lineata (Schneider) from chickens at Manhattan, Kansas, U.S.A., and Cambridge, England.

2. Eggs arising in the anterior ovary pass into the posterior uterus; similarly, eggs from the posterior ovary pass into the anterior uterus.

3. In young females eggs may be fertilised at any place in the uteri; in adults, fertilisation occurs near the distal ends of the uteri.

4. With the aid of a micromanipulator, a small structure in one pole of the mature egg, previously decribed as an opening, an opercular plug in the shell, or as an internal thickening of the shell, was found to be a solid, conical appendage of the vitelline membrane, free from the shell.

5. Fertilised eggs develop to the coiled embryo (infective) stage in 16 days when incubated in water at 30° C.; in 1 mm. of water at 33° C., they become infective in 10 days.

6. Water cultures of fertile eggs do not develop when kept at constant temperatures of 0° C., or of 10° C.; at 15° C., development proceeds.

7. Constant refrigeration of fertile eggs in water cultures for 1 month at 0° C. so lower the vitality that, on being incubated subsequently at 30° C., they divide slowly and soon die; keeping the eggs at 10° C. for 1 month has no deleterious effect on them when incubated subsequently at 30° C.

8. In hatching, the embryo may escape from any part of the egg shell, either in the duodenum of the host, or in water cultures; newly hatched larvae swallowed by the chicken seldom become established; infestation normally result from the ingestion of embryonated eggs.

9. The habitat of A. lineata is the duodenum, especially the portion which is a few centimetres posterior to the entrance of the bile ducts; determination of hydrogen-ion concentrations showed that the nematodes live in nearly neutral media (av. 6·7).

10. Penetration of the duodenal mucosa by larvae 10–17 days old is frequent in young chickens; occasionally, a larva goes on through the intestinal wall to the liver and lungs, but ordinarily, after the 17th day the young worms withdraw from the mucosa into the lumen of the intestine.

11. Young A. lineata grew to maturity in 50 days in chickens parasitised when about a month old; in six 8-day periods following hatching of the larvae, the average daily growth in length per period was about 0·12 mm. in the first period, 0·75 mm. in the second, 1·5 mm. in the third, fourth, and fifth periods, and 3mm. in the sixth period.

12. At least three moults occur before the adult from of the nematode is developed. Important morphological changes associated with the moults include: after first moult, presence of pre-anal swelling (males), and of anal prominence in both sexes; after second moult, lips with oral papillae and dentigerous ridges, projecting Iateral folds (alae) present in newly hatched larvae replaced by non-projecting lateral lines, females with vulva and shorter tail proportionately, and males with pre-anal sucker and three pairs of caudal papillae; after third moult, external characters similar to those of the adult A. lineata.

1. Two species of endoparasites, a Chalcid Stenomalus micans and a Braconid Coelineus niger, were found in every sample of “gouted” barley examined from a number of counties in southern England.

2. Chlorops infestations were severe in 1928 in many districts, and the majority of the “gouted” shoots were of winter-type damage, of which 68 percent. were parasitised, two-thirds by S. micans.

3. The larval anatomy of S. micans is described:

(a) There are five larval instars, each of which is described.

(b) The first larval instar appears to be partly predaceous.

(c) The larvae can be kept alive for 5 days on the surface of normal physiological saline solution and moulting occurs, which enables the instar to be determined with certainty.

(d) The tracheal system is devoid of spiracles until the fourth larval instar; spiracles then develop and are connected to the former rudimentary stigmatic trunks prior to the death of the host.

(e) The fourth instar larva develops a cephalic boring armature which is used for breaking up the internal organs of the host and also to bore an exit hole through the latter's body wall.

4. The pupa of S. micans is described and sex differences are indicated.

In 1928, a collection of marine fish trematodes was made at the United States Bureau of Fisheries Station at Beaufort, North Carolina; thirty-six of fifty-one species of fishes examined contained trematodes; only one or two specimens of some species were examined. Only Monogenea were collected from Elasmo branchs. The following report includes the digenetic forms identified. Type specimens of all new species are deposited in the United States National Museum.

Although Sarcocystis infections are very common in the muscle of mammals, and to a less extent of birds, in reptiles they have oniy rarely been seen. In a list given by Wenyon (1926) only two forms are recorded, namely from the muscles of Africaii geckoes and of the lizard Gongylus. The form here described was found in fairly large numbers in the striated muscle tissue of the Australian carpet snake Python spilotes. For the parasite the name Sarcocystis pythonis is suggested.