Rats were infected with doses of 100, 1000, 5000 and 10 000 eggs of Taenia taeniaeformis. Haemagglutinating antibody to cysticercus antigen was detected at the 4th week of infection. The appearance and levels of antibody titre did not vary greatly with the infective dose. An IgM peak appeared at the 6th week, with IgG appearing slightly later and continuing to rise. Transfer of serum from the 1st week onwards from infections with 1000 eggs however could confer significant protection. Dilutions of hyperimmune serum (1 ml volumes) of up to 1/32 conferred significant protection on normal recipients. Hyperimmune serum transferred up to 4 days before challenge could confer 80% protection whereas serum transferred 4 days after challenge was totally non-protective. The significance of this finding is discussed in the light of current knowledge of metacestode immunity.

The distribution of Ancylostoma caninum larvae in the various regions of the central nervous system of mice of previously uninfected or reinfected groups was studied. Although a dose of 4000 larvae was lethal, the distribution of larvae was not appreciable in the CNS. Many larvae were recovered from the cerebral hemispheres and cerebellum of infected mice whereas no incidence of eye involvement was observed in any mouse. In the reinfected mice groups there was a much lower recovery than in the previously uninfected groups in the latent period of study.

A striking was difference was found in the responses of Schistosoma mansoni and S. haematobium miracidia to the intensity and direction of light and to gravity. S. mansoni miracidia were found to be positively phototactic and sensitive to small changes in light intensities. They were indifferent to gravity. S. haematobium miracidia however were negatively phototactic and unable to distinguish low light intensities from darkness. They showed a strong positive geotaxis.

Both S. mansoni and S. haematobium miracidia could successfully find and infect snails to a depth of 2 metres of water: the significance of these findings in relation to transmission of schistosomiasis in the field is discussed.

Infective larvae of Brugia pahangi were irradiated at 10, 25 or 45 krads by means of a Cobalt 60 source. In cats, 10 krads caused the worms to be stunted and sterile but allowed them to become 5th stage, migrate posterioly into the afferent lymphatic, and produce pathology.

25 krads prevented the worms from developing beyond the early fourth stage and from migrating away from the popliteal lymph node. No gross pathological reactions were evident. 45 krads produced the same effects as 25 krads but the longevity of the worms was much reduced.

In cats infected with normal, or irradiated, infective (L3) larvae of Brugia pahangi counterimmunoelectro-phoresis revealed the presence of antibody to soluble antigens derived from microfilariae, adults and infective larvae of the same parasite. Infected cats with a persistently high to moderate microfilaraemia gave positive precipitin reactions to L3, microfilarial and adult worm antigens. Cats which had become amicrofilaraemic had antibody to L3 and microfilarial antigens but not to adult worm antigen. Serum from cats inoculated with irradiated L3 larvae produced a precipitin reaction only to the L3 antigen.

Enenterum elsti sp. nov. and E. prudhoei sp. nov. are described from the intestine of Neoscorpis lithophilus off Mapelane, Natal, South Africa. These species differ from others of the genus Enenterum in the ratio of the oral sucker to body-length and in the length of the prepharynx. E. elsti differs from. E. prudhoei in size, in sucker-ratio and in the number and configuration of the oral lobes. A key to the species of Enenterum is presented and the status of the genus briefly discussed.

Dioctowittus denisoniae n. sp. from Denisonia punctata differs from D. wittei and D. chabaudi in the smaller size, lack of vestigeal male precloacal sucker, short egg-filaments, the presence of lateral expansions at the posterior end in the male, and in the expansions of the oesophageal tissue between the stichocytes. Dioctowittus sp. from Liasis amethystinus differs from the three described species in the possession of lateral lobes at both extremities.

Polyonchobothrium scleropagis (Cestoda: Pseudophyllidea) is described as a new species from the Australian osteoglossid fish Scleropages leichardti Günther.

Phaneropsolus aspinosus sp. n. is described from the leaf monkey Macaca fascicularis in central Pahang, West Malaysia. Morphological characteristics are compared with both the subgenera Phaneropsolus and Primatotrema.

Histochemical observations have been made on the localization and distribution pattern of succinate dehydrogenase (SDH) in the lymphatic system of Ceylonocotyle scoliocoelium by employing tetrazolium nitro BT. The enzyme activity appeared in the form of diformazon granules which are believed to consist of mitochondrial aggregates. It is further suggested that this enzyme helps in the transportation of the metabolites. This is the first report of SDH in the lymph channels involving transportation.

The genus Paraheterotyphlum is upheld, the type species, australe Johnston and Mawson, 1948, is redescribed from the type material and compared with specimens collected from the following sea snakes from Australian waters: Pelamis platurus, Hydrophis elegans, Aipysurus laevis, Astrotia stokesii, Disteira kingii. These specimens were also compared with specimens from Laticauda semifasciata and colubrina from Taiwan waters.

Two species are differentiated: P. australe and P. ophiophagos Schmidt and Kuntz, 1973 mainly by the larger and more distinct interlocking facets on the lips of the latter species. Third and fourth stage larvae, probably of P. australe are described and the distribution and affinities of these species is discussed.