AND ANOTHER ALLIED ORGANISM. 53 



to develope in a way not clearly traced into a sporocyst contain- 

 ing a large number of cercarice, sometimes all well formed, some- 

 times found in various stages of growth ; these are set free from 

 the nurse and the host in a way not clearly made out, and are 

 then found as freely moving organisms which attach themselves 

 to the outside of a snail, become encysted, and ultimately develope 

 into sexual Trematodes, whose eggs start in the same round again, 

 thus forming a complete case of alternation of generation. 



Such a history as I have sketched was supposed to apply to 

 B. polymorphus somewhat modified, differences of opinion, how- 

 ever, existed on some points, and M. Lacaze-Duthiers, after 

 alluding to them, goes on to say " that it is still permissible to 

 employ the name Bucephalus, given by Baer, while waiting for 

 clearer light as to the transformations of this being ;" he accor- 

 dingly names one of the organisms I bring before you to-night, 

 Bucephalus Haimeanus, after his friend M. Haime, and describes 

 the tubular structure in which they are found as sporocysts or 

 nurses. This structure I have always found branched, as shown 

 in the diagram. M. Lacaze-Duthiers says of it, " Taken out of 

 the organs they unwound in long white filaments, which were very 

 fragile, so tbat it was very difficult, I might say almost impossible, 

 to obtain an entire one, so as to be able to examine its ex- 

 tremities." Tbey are doubtless very fragile. I have never seen 

 them unwind as described, but have found it necessary to teaze a 

 portion out with needles in water, to get any good idea of its 

 nature, and it was in this way that I found the bifurcations so 

 evident, and in certain cockles where there were egg sacs these 

 appeared attached as in the diagram ; when examining these under 

 the microscope I came to the conclusion that the sacs were 

 anatomically united to the tubular structure. On the supposition 

 that we are dealing with cercarian sporocysts, this appearance may 

 doubtless have arisen from such sporocysts being contained in the 

 genital ducts. 



The striation perpendicular to the axis, as described by M. 

 Duthiers, is evident in well developed portions of the tube, such 

 portions when ruptured expel their contents with considerable 

 vigour, but I have never observed any other kind of movement. 



M. Duthiers gives an account of an appearance of budding, 

 which is figured in the diagram, this I have often seen, and 

 interpreted it from my point of view as the remains of a short 



