1. Evidence from previous literature shows that puppies are commonly infected with larvae ofToxocara canisat birth and that prenatal infection can be produced by feeding embryonated eggs to pregnant bitches.2. Observations on fifty-eight dogs in Brisbane showed that all of twenty-nine puppies 1–6 months old were infected, while only three out of twenty-nine dogs over 6 months old were infected.3. In naturally infected puppies, 1–3 weeks old, it was found that at birth third-stage larvae were present in the lungs. Third-stage larvae continued to appear in the lungs for the first week of life; their length was 0·6–1·3 mm.4. Third-stage larvae were found in the stomach on the day after birth; at 3 days after birth fourth-stage larvae were found in the intestine.5. It appeared likely that the second moult occurs in puppies before birth, and that the third moult takes place at a length of 1·0–1·3 mm. in the lungs and stomach within the first week of life.6. By the beginning of the second week, fourth-stage larvae were fully grown and had commenced the fourth moult at a length of 5–7 mm.7. Throughout the second and third weeks, adults grew rapidly, reaching a length of about 67 mm. by the end of the third week, but no eggs had appeared in the faeces at this time.8. Experimental infection of mice with eggs showed that the larvae were distributed to the somatic tissues, few reaching the alimentary tract. The larvae did not progress beyond the second stage in the tissues of mice.9. Experimental infection of dogs with eggs showed that in dogs over 5 weeks old the larvae were distributed to the somatic tissues and did not reach the alimentary tract. The larvae did not progress beyond the second stage, though some of them showed signs of commencing the second moult. In contrast, 1 to 3-week-old puppies infected in the same way were found to harbour larvae in the alimentary tract. Though some of these larvae were probably derived from a naturally acquired prenatal infection, it was evident from the progress of development that the experimental infection resulted in the presence of second-stage larvae in the liver and lungs and that these larvae underwent the second moult, commenced development as third-stage larvae in the lungs, migrated into the stomach and developed to the adult stage in the intestine.10. Experimental infection of dogs and foxes with mice harbouring second-stage larvae in the tissues showed that, in some instances, development of larvae proceeded in the alimentary tract. No evidence of somatic migration was found in dogs infected in this way, but in foxes second-stage larvae were found in the lungs.11. The structure and development of the second, third and fourth stage is described in detail and found to resemble closely the development ofT. catilarvae (Sprent, 1956). Second-stage larvae from dog tissues had a length of 0·34–0·44 mm. and the second moult occurred at a length of 0·37–0·44 mm. Third-stage larvae varied in length from 0·46 to 1·36 mm., and the third moult occurred at a length of 0·98–1·3 mm. Fourth-stage larvae measured 1·2–6·3 mm., though moulting fourth-stage larvae were observed up to a length of 7·4 mm. Sexual differentiation occurred during the fourth stage and was evident at a length of about 1·5 mm.12. The migratory behaviour of the larvae ofT. canisandT. catiis compared and discussed in relation to their wide range of hosts. It is concluded that differences in migratory behaviour are adaptations to prevailing modes of nutrition and it is suggested that the somatic migration occurring in dogs is an adaptation to the non-predatory habits of this particular host.

1. An account is given of the history, synonymy and host-range of Toxocara cati.2. Eggs of T. cati were fed to various animals, and the second-stage larvae were found in the tissues of earthworms, cockroaches, chickens, mice, dogs, lambs and cats.3. Cats were successfully infected by feeding eggs of T. cati and by feeding mice harbouring larvae in the tissues.4. In egg-infected cats the larvae were found in the liver, lungs, muscles and tracheal washings as well as in the digestive tract, indicating that they migrate through the tissues.5. In mice the larvae were found in the liver, lungs and muscles, but did not reach the alimentary tract. Changes occurred in the mouth region of the larvae in mouse tissues between 8 and 11 days after infection, but no actual moult was observed. No significant growth of the larvae was observed in mouse tissues.6. In mouse-infected cats the larvae were mostly confined to the wall and contents of the digestive tract.7. It appeared that the second moult occurred in the stomach wall of egg-infected cats at 3–10 days after infection; moulting larvae measuring 0·353–0·423 mm. in length; in a mouse-infected cat moulting larvae (length 0·459–0·765 mm.) were observed at 6 days after infection.8. In both egg- and mouse-infected cats the third-stage larvae grew in the stomach wall and moulted for the third time at a length of 0·9–1·2 mm. This occurred at about 10 days in mouse-infected cats and at about 19 days in egg-infected cats.9. The smallest fourth-stage larvae were found in the stomach contents whence they passed into the intestine. Probably they are at first attached to the wall and later become free in the intestinal contents.10. The fourth-stage larvae have lips resembling the adult; sexual differentiation occurs during this stage, being first evident at 1·5 mm.11. The fourth moult occurs in the intestine at a length of approximately 4·5–5·5 mm.12. In the adult stage the lateral alae gradually disappear and the cervical alae reach the adult form at a length of approximately 45 mm. The smallest female observed containing eggs in the vagina measured 55 mm. in length. Eggs were first observed in the faeces at 56 days after infection by eggs.13. The evidence from experimental and natural infection indicated that infection of cats with T. cati always takes place after birth.14. No larvae were found in the alimentary tract of dogs following experimental infection either with eggs or with infected mice.15. The relationship of the life history of T. cati to that of other ascaridid species, to the feeding habits of the definitive hosts, and in relation to the occurrence of human infection with this parasite is discussed.

No abstract

The family Ascarididae, as defined by Hartwich (1957) and emended by Osche (1958), comprises species in the generaAscaris, Toxascaris, ParascarisandLagochilascaris, all occurring in terrestrial mammals. Other ascaridoids of terrestrial mammals occur in Crossophoridae and Toxocaridae, the latter includingToxocaraandNeoascaris(see Hartwich, 1957; Sprent, 1957; Osche, 1958).

The genus Ophidascaris is revised and divided into five groups of species. A key for the species groups is provided. Group 1 (' filaria' group) occurs in pythons and a key is provided for differentiating eight species based on fresh and preserved specimens and on developmental patterns. 0. papillifera (Linstow, 1898) is redescribed from the type-specimens and is considered to be close or identical to 0. niuginiensis, for which Candoia carinatus is recorded as a new host. A key for the differentiation of species in Groups 2 to 5 is based on preserved specimens only. Group 2 (' obconica' group) contains (i) 0. obconica and 0. trichuriformis [ = caballeroi] in South American colubrids (further investigation will probably show that 0. trichuriformis is a synonym of 0. obconica); new host records are Xenodon severus, X. neuwiedii, X. colubrinus, Leptodeira annulata, Thamnodynastes pallidus, Leimadophis poecilogyrus and Boa constrictor; (ii)O. ashi n. sp. (new species name for ' 0. labiatopapillosa' ) in North American colubrids, new host records are Nerodia valida, Heterodon nasicus and Storeria occipitomaculata; (iii) 0. mombasica in African colubrids; new host records are Psammophis phillipsii and P. sibilans; (iv) 0. solenopoion in Madagascan colubrids; (v) 0. pyrrhus in Australian elapids; new host records are Cacophis squamulosus, Cryptophis nigrescens, Demansia atra, D. olivacea, Hemiaspis signata, Hoplocephalus bitorquatus, H. stephensi, H. bungaroides and Tropedechis carinatus, it is also recorded in Australia in the colubrid Styporhyncus mairii (new host record) and in Demansia papuensis papuensis and D. olivacea papuensis in Papua New Guinea; (vi) 0. piscatori in Asian colubrids; (vii) 0. excavata [? = schikhobalovi] in Agkistrodon spp. and possibly other aquatic snakes in Asia; new host record is Agkistrodon halys blomhoffi. Group 3 (' radiosa' group) in African viperids contains 0. radiosa [= intorta] in Bitis spp. Specimens from Atheris nitschei, Causus rhombeatus and the colubrid Boaedon lineatus were similar, but showed differences indicating possibility of other species in this group. Group 4 (' najae' group) in African elapids and Asian elapids and colubrids contains 0. najae [ = daubaylisi]; new host records are Ophiophagus hannah, Boiga cyanea, Elaphe carinata. Group 5 (' arndti' group) in South American crotalids and colubrids contains 0. arndti [ = travassosi and sprenti] in Crotalus spp. and Bothrops spp.; new host record is B. atrox in Panama. No morphological differentiation except size could be detected between 0. arndti in crotalines and 0. sicki in colubrids, but in view of difference in the feeding habits of their host, both species names were tentatively sustained; new host records for 0. sicki are Xenodon neuwiedii, Leimadophis poecilogyrus, Pseudoboa cloelia, Philodryas patagoniensis and Micrurus frontalis; 0. ochoteranai was regarded as a species inquirenda.