THK VICTORIAN NATURALIST. 



•25 



A slight jerk, and the extended filament is rapidly contracted till 

 it assumes a state of rest. Although of such length, it does not 

 take up much space, since it arranges itself in coils which overlap 

 each other. A gas-globule is usually present at the extreme tip. 

 The nurse-sacs of this form are very long compared with typical 

 ones, being crowded with cercarige, and are present in great 

 numbers in the " liver " of the host. 



In the last note reference was made to the occurrence of cysts 

 within the snails and the comparative absence of encystation 

 outside the snail was commented upon. The appearance and 

 structure of these cysts will be described in the present note. 

 Seven varieties have been observed, and there is every 

 reason to believe that they are the temporary home of distinct 

 forms of fluke embryos. Rabbits and ducks have been fed upon 

 some of them, but up to the present no satisfactory results have 

 been obtained. However, the experiments cannot be regarded 

 as conclusive, since the material operated upon has been of too 

 limited a character to found upon it any definite conclusions. 



The first cyst to be de- 

 scribed is that occurring 

 in very large numbers in 

 Isidora texturata, Isidora 

 alicice, and Limnea lessoni. 

 It reaches a size of T ^ of 

 an inch, and is easily known 

 by the curious appearance 

 of some glassy-lookingcells, 

 which are always arranged 

 in a very definite manner. 

 In the cercaria these cells 

 stand out quite distinct 

 from the rest, and are seen 

 as a band extending down 

 each side of the body. 

 When the animal is about 

 to encyst it doubles the 

 anterior of its body over 

 the posterior portion, and 

 throws off the tail. This 

 doubling is not quite equal, 

 so that darkish cells in the 

 upper fold do not lie quite 

 above those in the lower, 

 but rather a little to one 

 side. Two loops, therefore, 

 of these specially modified 



FIG. I 



Wn IN. 



FIG, 3 



FIG. 6 



Cysts of Fluke Embryos. 



cells are seen (fig r). It was not till actual encystation had 



