[ 349 ] 



XVIII. Further Observations on Entozoa, loith JExperiments. By T. Spencer Cobbold, 



M.D., F.L.S.* 



Read December 20th, 1860. 



Although, since my last communication, I have had fewer opportunities of examining 

 Entozoa, I think it will be admitted that the new or otherwise important forms which 

 have come under my notice, are of sufficient interest to be placed on record, in continu- 

 ation of the series of papers previously submitted to the Society. 



In the present instance, the number of different animals specially examined with refer- 

 ence to the presence or absence of internal parasites, amounts in aU to forty-three, in- 

 cluding seven fish, two reptUes, seventeen birds and nineteen mammals. Of these only 

 three fish, one reptile, seven bu'ds and the same number of mammals, were found infested. 

 In so far as these numbers refer to species formerly living in the Zoological Society's 

 menagerie, the proportion is small, and tends to confirm both the statement and explana- 

 tion which I have before hazarded in respect of the comparative freedom from internal 

 trematode parasites, found to obtain in foreign animals subjected to a condition of 

 captivity, 



1. DiSTOMA CONJUNCTUM (mihi). 



Distoma conjunctum, Cobbold, Linu. Soc. Proceed, vol. v., Zool. Div. p. 8. 



Bemarlcs. — As already briefly indicated in my synopsis of the DistomidEe, published in 

 the Society's Proceedings {loc. cit.), this species of fluke infests the liver of the American 

 Red Eox {Ccmisf ulcus). The animal in question died at the Zoological Society's Gardens, 

 Eegent's Park, in December, 1858, and was dissected on the 24.th of that month, the carcase 

 being still quite fresh. The biliary ducts were found thickened and enlarged in several 

 places, forming here and there small cysts of variable size. In these cavities — partly occu- 

 pied by purulent matter — the distomes were lodged ; and when placed in water they showed 

 signs of life. Their extreme transparency at once displayed, under the microscope, the rela- 

 tive position and degree of development of the various organs, as shown by the accompany- 

 ing figure (fig. 1, Plate XXXIIL), in which I may particularly remark the great breadth of 

 the digestive ceeca, the well-defined excretory canals passing transversely inwards from the 

 botryoidal albumen-forming glands (Dotterstock), and also the large yelk-forming organ 

 or ovary (Eikeimstock), placed in the centre of the body, immediately below the uterine 

 folds. A still more noticeable feature, however, is seen in the unusual length and breadth 

 of the contractile vesicle belonging to the excretory system. It occupies fully one-third 

 of the longitudinal diameter of the body, and bifurcates at the summit, the course of each 

 division being traceable almost as far forward as the bulb of the oesophagus ; below, it is 

 suddenly constricted, and terminates, as usual, by a small central aperture. The sac itself 



* An abstract of this paper has been published in the Society's Proceedings, Zool. Div. vol. v. p. 255. 



3 a2 



