ON THE DEVELOPMENT OF LICHENOPORA VERRUCARIA. 129 
I have formerly brought forward certain evidence (7) tending 
to show that the formation of brown bodies is, to a large extent, 
a kind of excretory process, and it would be surprising if 
Lichenopora were altogether exempt from the necessity of 
forming brown bodies, whatever their function may be. The ° 
explanation of the apparent anomaly of the absence of these 
structures appears to me to be that parts of the alimentary 
canal degenerate during the functional activity of the poly- 
pide. A newly formed polypide has the inner border of the 
epithelial cells of its alimentary canal clear and sharply defined. 
Parts of the alimentary canal of old polypides are in the same 
condition, but certain parts of the cecum of the stomach are 
in a very different state. The cecum is coloured during life 
with the pigment which is so characteristic of parts of the 
alimentary canal in Polyzoa. In sections these parts contain 
a very small quantity of protoplasm, and consist principally of 
yellowish granules which are very similar to the granules which 
largely compose the brown bodies—that is to say, there is no 
very great difference between the latter and those parts of the 
alimentary canal which are pigmented during life. I believe 
that this implies that excretory substaces accumulate in the 
epithelium of the alimentary canal as the polypide grows older. 
In the case of the younger colonies the entire polypide usually 
atrophies in course of time ; but in the case of older colonies, 
in which it is of the utmost importance that every zocecium 
should be contributing its share towards the nutrition of the 
ovicell, the excretory granules are discharged into the stomach 
continuously during the life of the polypide. 
The facts are that the alimentary canal of these poly pides 
usually contains solid substances which resemble fragments of 
brown bodies—that certain parts of the epithelium have no 
definite inner limit, but pass off into a cloud of granules which 
extend into the alimentary canal, and that the polypides are 
usually distinctly larger than those of young colonies. It is 
not always easy to get polypides (in sections) which are well 
orientated for the purpose of measurement ; but the measure- 
ments I have been able to obtain support the impression one 
VOL, 39, PART 1.—NEW SER. I 
