LIFE-HISTORY OF BUCEPHALUS HAIMEANUS. 657 
hematoxylin, these cells, in cercariz in which the cuticle had 
not yet formed, were stained a very deep blue. In other 
cercariz (on the same slide) in which the cuticle was present, 
the cells were stained only slightly, while the cuticle had 
taken the stain deeply; the reaction of the substance within 
the cell toward the stain in the one case, and of the cuticle in 
the other, being identical. 
By reason, therefore, of all the evidence which I have been 
able to gather from my observations on B. haimeanus I 
have been led to believe that the outer body layer, in this 
case, is a secretion of the more or less deeply lying gland 
cells. 
Although working upon a form very similar to that upon 
which Ziegler based his belief that the Hautschicht repre- 
sented a metamorphosed cellular epidermis, I have reached a 
different conclusion. The more precise modern technical 
methods probably account for this. 
The only cellular body covering present at any time is that 
which I have already described as being formed at the seven- 
cell stage. This enveloping membrane increases in size as the 
embryo grows, always being closely applied to the surface of 
the syncitium which forms the body of the larva. At no time 
in the development or in the later history is a definite, com- 
plete epidermis to be seen. The nuclei of the parenchyma- 
tous tissue may form a more or less regular row, between 
which cytoplasm may be demonstrated, but the cell walls of 
a continuous epidermis are never visible. 
As has been already indicated, it is possible, in a series of 
sections through a well-filled germ tube, to obtain embryos 
in every stage of development. ‘his being the case, if any 
portion of the body covering were thrown off during these 
larval stages, some evidence of the process would be seen. 
In no case whatever have I seen anything which would lead 
me to suppose that such a process took place in the embryonic 
stages of Bucephalus. 
My evidence, therefore, seems to confirm the observations 
of Blochmann, Kowalevski, and others rather than those of 
Ziegler, Biehringer, Schneider, Kerbert, etc. 
