Identification of members of the family Schistosomatidae presents problems not only because of the imperfect state of their taxonomy, but also because no attempt has been made to collect and organise the available data. There are only two general keys on the schistosomes (Price, 1929 ; Yamaguti, 1958) both of which are incomplete. The result of this is that many authors, too numerous to mention, list genera which are no longer valid and erect new species without comparing them with species to which they are obviously closely related.

About 100 specimens of the fresh-water snail, Melanoides tuberculatus (Muller), collected on 30th March, 1962 from “Kukrail”, a tributory of river Gomati, were examined for larval infection. One specimen was found infected with a unique cercaria belonging to the genus Transversotrema. The writer subsequently attempted to collect this cercaria from the same place and 1750 specimens of the said host were examined in the following years (1962–67) without success. Further, a large number of specimens of fishes of the genera Channa Gronov; Colisa Cuv. and Val.; Xenentodon Regan and Nundus Cuv. and Val., common in the tributary were also examined for metacercarial infection of this cercaria but none were found.

The epidemiology of parasitic infections may be profoundly influenced by infra-specific variations in infectivity for either intermediate or definitive hosts. Such variations will decide the basic ecology of the host-parasite relationship, and variations in virulence and pathogenicity therefore determine different patterns of disease. While some of the evidence of infra-specific variations has been derived from experimental studies, much of it has been recorded by those concerned with investigations of the epidemiology and transmission of parasitic infections and the practical aspects of their control. The unequivocal demonstration of genetic heterogeneity of certain parasites of medical importance has therefore resulted in a better understanding of their epidemiology and, in some cases, is leading to greater precision in attempts to control them.

Two dicrocoeliid trematodes are reported from Ghana. Concinnum ghanensis n.sp. is from the gall bladder and bile duct of the Senegal kingfisher, Halcyon senegalensis (L.), differing from the 14 species recognized in the genus in body shape, the caeca terminating at the vitellarian level or just previtellarian, and the vitellaria being in the form of a band of follicles extending across the body. Dicrocoelium hospes Looss, 1907, is from the bile duct of the Sudan sheep.

The life cycle and biology of T. deminutus were studied and investigations were carried out on the site of infection in the host, the female to male ratio, the egg laying capacity of the female worms, the development of the eggs after leaving the host and preliminary observations on the effects of desiccation and low temperatures on the third stage larvae were made.

Descriptions of four new tylenchs belonging to different genera are given : (1) Tylenchus (Tylenchus) holochmatus n.sp., (2) Tylenchorhynchus varicaudatus n.sp., (3) Trichotylenchus trilokiae n.sp., (4) Helicotylenchus pteracercus n.sp. The material of the first described species was collected in North India and that of the other new species in South India. Systematic features of new species are fully discussed and compared with those of the related forms.

Detailed descriptions are given of Tylenchorhynchus digitatus and Pratylenchus indicus described by Das (I960) from Hyderabad. The material was collected from type locality but from different hosts. Tylenchorhynchus curvus Williams, 1960, is recorded from India.

Species reported as causing damage to economically important plants in Hyderabad are : Hoplolaimus seinhorsti Luc, 1958, parasitic in cauliflower; Pratylenchus thornei Sher and Allen, 1953, parasitic in maize and Rotylenchulus reniformis Linford and Oliveira, 1940, parasitic in grape vines.

Ichthybothrium ichthybori gen. et sp. nov. (Pseudophyllidea : Ptychobothriidae) is described and figured from specimens collected from the intestine of the African freshwater fish Ichthyborus besse from the White Nile near Khartoum, Sudan. Ichthybothrium and Ptychobothrium show some similarities but can be differentiated by the shape of the scolex and the position of the vitelline follicles. Ptychobothrium cypseluri Rao, 1957 and Plicatobothrium cypseluri Cable and Michaelis, 1967 are congeneric and a new name Plicatobothrium raoi is proposed for the former.

1. Individual chemical estimations of the glycogen concentration of the digestive gland and the foot were made on 272 uninfected L. littorea and 395 L. littorea infected with larval Digenea from Scalby Rocks, North Yorkshire, during the period from September 1966 to November 1967.

2. The glycogen concentrations of the digestive gland and the foot of both infected and uninfected L. littorea showed pronounced seasonal changes, being highest during the autumn and lowest in the spring. Infected L. littorea had less glycogen in the digestive gland and foot than had uninfected L. littorea, and the amount of reduction was characteristic for each of the three species studied, namely Cryptocotyle lingua, Renicola roscovita and H. leptosoma. Infection with C. lingua caused greater decrease in the glycogen concentration of the digestive gland, while infection with R. roscovita had a more marked effect on the foot. The effect of infection with H. leptosoma and with concurrent infections with two species are described and considered.

3. The seasonal changes in the amount of glycogen in the digestive gland and the foot of uninfected and infected L. liitorea are considered in relation to seasonal reproductive changes and the ecology of the host at Scalby Rocks.

The varying susceptibility of local races of bulinid snails to different strains of Schistosoma haematobium has been recorded by many workers including Le Roux, 1954; Cridland, 1955, 1957; McCullough, 1957, 1962; Wright, 1962, 1963; Cowper, 1963; Pitchford, 1965 and Paperna, 1968. The respective species groups of snails referred to are those created by Mandahl-Barth (1958). As a result of his experiments Le Roux (1958) suggested that there are two separate species of parasite, the form transmitted in North Africa by the truncates group of snails being known as S. haematobium and that developing in Africa south of the Sahara in the africanus species group as S. capense (Harley, 1864), a view which has been supported by many workers.

Blood containing microfilariae has been successfully transported from various laboratories to London. This blood was used to infect mosquitoes with filarial parasites by means of a membrane feeding system. Brugia malayi, Wuchereria bancrofti and Dirofilaria immitis have been successfully transported in this way.