LIFE-HISTORY OF BUCEPHALUS HAIMEANUS. 653 
ments of the tails, are pushed out (fig. 9, ¢.). Their further 
development consists chiefly in an elongation, during the 
process of which the middle piece, which is formed from the 
basal portion of ‘each branch, assumes definite form (fig. 13, 
ir.). 
The remaining organs of the mature cercaria, which, with 
the exception of the nervous system, of the gut, and of the 
water vascular system are extremely rudimentary, are mean- 
time being gradually differentiated from the general syn- 
cytium which composes the body of the larva (fig. 13). 
This appearance can best be described under the section 
immediately following which deals with the structure of the 
older cercaria. 
Before proceeding to this section I wish to speak of the 
the recent investigations of Reuss (41, 1903) on the develop- 
ment of the cercaria and sporocysts of Distomum dupli- 
catum, and of those of Haswell (23, 1903) on the sporocysts 
of an Echinostomum. 
Both of these papers reached me after the completion 
of my investigations on the sporocysts and cercaria in 
Bucephalus. It gives me pleasure to note that my observa- 
tions confirm those of Reuss in every respect. With the 
observations of Haswell they are also in accord in nearly 
every particular. 
Tue ANAToMY oF B. HAIMEANUS. 
The body of Bucephalus (fig. 1) is somewhat lance-shaped, 
varying in length in various individuals from 015 mm. to 
0:20 mm., and in breadth from 0:04 mm. to 0°08 mm.; the 
thickness is but slightly less than the breadth. 
The anterior end of the body is slightly pointed, termina- 
ting in a three-lipped invagination which is described as the 
mouth by the older investigators. The posterior end of the 
body terminates bluntly and passes abruptly into the tail, 
which consists of a median portion and two lateral append- 
ages, 
