406 



MR. G. M. VEVERS OX KNTOZOA FROM ANIMALS 



the length of life of parasites of various groups in their hosts. 

 Very little reliable information has been gathered on this im- 

 portant point. The evidence given by the incidence of parasites 

 which have intermediary hosts is, of course, more trustworthy 

 than that of forms which have a simple life-cycle. In the latter, 

 infection is accumulative, and may either be acquired in the 

 paddock or be brought into the Gardens on food : thus nine 

 examples of Gastrodiscus cegi/ptiacits were found in a Grevy's 

 Zebra which had been in the Gardens for six years. This parasite 

 normally occiu'S in Africa, and requires as an intermediary host 

 a freshwater mollusc [Cleopatra hidimoides) which has not been 

 recorded from Europe. There can be no doubt, then, that the 

 specimens found had actually lived in the Zebra since it came 

 from Africa, and were, therefore, over six years old. 



In the same Zebra were a number of species of Bursate 

 Nematodes, some of which have been recorded both from Africa 

 a,nd Europe. The life-cycle here is a simple one. That it is not 

 possible to draw trustworthy conclusions in such a case is well 

 illustrated by the findings in an Onager [Eqims onager^ which 

 died quite recently. A number of the same species of parasites 

 which occurred in the Zebra were found in this Onager, which 

 had been born in the Gardens. 



Two of the species of Cylichnostomes in the Grevy's Zebra had 

 not been previously recorded, and it is possible that these were 

 originally imported, but the infection may have been renewed 

 in the pa.ddocks. In this connection it is noteworthy that a 

 Chapman's Zebra which died last year, after nine years in the 

 Gardens, had only species of Bursate Nematodes which occur in 

 European Horses. 



We have, as another example of the conta.minative group which 

 might accumulate in the Gardens, an apparently unrecorded 

 species of Atractis in the Elephant. Many specimens of this 

 Nematode were found in the Indian Elephant which died in 

 December last and which had been in the Gardens for twelve 

 years. Recent examination of the faeces of the Elephant living 

 in the next paddock showed that this one also is heavily infected. 



The minute but fully mature females of Atractis are passed 

 from time to time in the faeces, and these contain embryos so far 

 advanced as to have the adult form. If these embryos are 

 discharged by the mother worm in the intestine of the host, 

 it is conceivable that they might attain sexual maturity almost 

 immediately, and would then provide an exception to the general 

 rule that parasitic worms do not produce a second generation of 

 adult forms within the body of their definitive host. 



The following points of especial interest were noted in 

 individual species of Parasites ; — 



Two specimens of Gnatliostoiaa spinigerum were obtained from 

 the stomach of a Leopard Cat {Felis hengalensis). A dissection 

 of the head-parts of a still living worm showed that the neck- 

 glands are hollow aiul contractile, and contain a fluid which plays 



