8 
The anatomical structure of Ceratoplana. 
It will suffice here to treat more thoroughly only the structures 
of the genital organs, as in its general organization this Polyclad 
genus resembles that of the genus Stylochoplana. A few features, 
however, deserve to be described. The description below refers, 
unless specified to the contrary, to C. colobocentroti. 
Body-Wall: The ventral epithelium near the margin is con- 
siderably thickened with numerous glandular cells containing a 
granular, eosinophile secretion. As I have mentioned before on 
various occasions, this secretion is of importance in aiding the 
animal in adhering to the substratum. It is, therefore, to be ex- 
pected that this peripheral glandular held should be well-developed 
in a species found in localities exposed to the strong action 
of the surf. The musculature of the body-wall is unusually thick 
and, for a Leptoplanid, of almost enormous strength. In the lateral 
parts of the body, the dorsal and ventral muscularis takes up nearly 
Vs of the space inside the basement membrane. The inner longi¬ 
tudinal muscular layer on the ventral side is, of course, the most 
powerful. But underneath the pharyngeal pocket it becomes so 
much thinner that the inner transversal muscular layer of the 
body-wall is a great deal thicker than it. It should also be ment¬ 
ioned that on the dorsal side the transversal muscle fibres, ar- 
ranged in a single row and lying immediately below the basement 
membrane, are unusually thick. The dorso-ventral muscular bundles 
are so strongly developed that the parenchyma becomes insignifi- 
cant. This prominent feature is, of course, also due to the great 
quantity of intestinal-branches, genital giands, and embedded gland¬ 
ular cells and the thickness of the ventral net-work of nerves, 
The unusual strength of the muscles must, of course, be connected 
with the occurrence of the animals near or in breakers. The whole 
body assumes the character of a single large adhesive disc, and 
the above-mentioned submarginal glandular layer confirms this im- 
pression. The whole body is thus well adapted for attachment 
to the substratum. 
Digestive system: The mouth is located near the hinder edge 
of the pharyngeal pocket. As a result of the splendid development 
