TREMATODA 



51 



regular markings do not undergo alteration during the con- 

 tractions of the body of the larva. 



A highly developed water-vascular system exists in these 

 little animalcules. On many occasions I saw traces of this set 

 of vessels, and in several instances I obtained a most satisfactory 

 view of the entire series of branches. 

 Anxious to receive confirmation of my 

 discovery, I demonstrated the existence 

 of these vessels to a skilled microscopist 

 the late Mr J. G. Pilcher, of H. M. 

 Army. In the briefest terms it may 

 be said that the water- vascular system 

 of Bilharzia, in the larval condition, 

 consists of two main stems, which 

 pursue a tortuous passage from head to 

 tail, and which, in the course of their 

 windings, give off several anastomosing 

 branches (fig. 19). As also obtains in 

 the corresponding larvae of Diplodiscus 

 subclavatus, there is no excretory outlet 

 visible at the tail. 



Encouraged by the experiences and 

 determinations of Pagenstecher, Filippi, 

 Wagener, Leuckart, and others, I sought 

 for the intermediate hosts amongst 

 fresh-water mollusks and small crus- 

 tacea. Failing of success in these, it 

 occurred to me that the larvae of Bil- 

 harzia might normally reside in fluviatile 

 or even in marine fishes. This latter 

 idea seems also to have struck Dr 

 Aitken. In an appendix to his ' Report Fr f 

 to the Army Medical Department for 

 1868/ dated from Netley, Nov., 1869, 

 he gives a figure of a nurse-form, which he terms a cercaria, 

 from the tail of a haddock suggesting for Bilharzia some 

 genetic relation. Dr Aitken also extends his views in reference 

 to certain larval trematodes alleged to have been found in the so- 

 called Delhi boils and Lahore sores. These parasitic forms have, 

 however, been shown by Dr Joseph Fleming to be nothing more 

 than altered hair-bulbs ('Army Med. Reports/ 1868-69). 



In regard to the flukes from the haddock, I have satisfied 



Ori s inal - 



