750 ON THE DEVELOPMENT OF BILHARZIA HiEMATOBIA. 
the presence of a highly developed water-vascular system in 
these little animalcules. On many occasions I saw traces of 
this set of vessels; and in several instances I obtained the 
most satisfactory, not to say beautiful, views of the entire 
series. Anxious to] receive confirmation of my discovery, I 
demonstrated the existence of these vessels to a skilled 
microscopist—Mr. J. G. Pilcher, of H.M. Indian Army— 
who expressed himself perfectly satisfied as to the correctness 
of my interpretation of their true character. 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. w). As also obtains in the corresponding 
larvae of Bijplodiscus subclavatus, there is no excretory outlet 
visible at the caudal extremity. 
Experiments. —Encouraged by the experiences and de¬ 
terminations of Pagenstecher and Wagner among the Trema- 
toda, and also more particularly by the remarks of Leuckhart 
in connection with Bi-stoma lanceolatum, and his success with 
the larvae of Bchinorhynclms , I naturally sought for the possible 
intermediary bearers of Bilharzia among fresh-water molluscs 
and small Crustacea. Failing of success in these, and quite 
independently, it occurred to me that the larvae of Bilharzia 
might normally reside in fluviatile or even in marine fishes. 
This latter idea seems also to have struck Dr. Aitken almost 
simultaneously. In an appendix to his Report to the Army 
Medical Department for 1868, dated from Netley, November, 
1869, Dr. Aitken gives a figure of a nurse-form, which he 
terms a cercaria, from the tail of a haddock—suggesting for 
Bilharzia some genetic relation of this sort, and also extending 
his views in reference to certain larval trematodes found in 
and extracted from the so-called Delhi boils and Lahore 
sores. Figures of the parasitic forms last referred to, and 
obtained from different persons, are given by Dr. Aitken, 
from drawings supplied by Dr. Joseph Fleming, of H.M. 
Indian Army, who had sent them from Meean Meer, in the 
Punjab, North India. In regard to the juvenile flukes from 
the haddock, I may say that I have thoroughly satisfied my¬ 
self that these well-known immature trematodes from the 
nerves of the cod-tribe can have no genetic relation with 
Bilharzia; and I think it due to Dr. Maddox to say that I 
accept his conclusion respecting them. In his admirable 
paper (. Microsc . Trans., vol. xv, 1867, p. 87), he offers strong 
proof to the effect that the so-called Bistoma neuronaii Monroii 
