CEPHALIC APPENDAGES OF GYMNOSOMATOUS PTEROPODA. 497 
shorter ones. When these prolongations arrive at the longitu- 
dinal muscular layer their contents change their appearance 
and present themselves under the form of a fibroid secretion 
(fig. 18, c) which absorbs much haematoxylin. These fibroid 
prolongations pass between the groups of longitudinal nmscular 
fibres ( d } fig. 13), traverse the layer of circular muscles, and 
pass into the reticulum of subepithelial connective tissue ; 
afterwards each prolongation penetrates into an epithelial cell, 
which it traverses by passing between the membrane and the 
cellular contents. 
3. Epithelial Investment. — This is the most character- 
istic part of the buccal cones of Clione. The epithelial cells 
are united in a variable number, so as to form an infinity of 
small circular groups on the surface of the cones. It is these 
small groups which give to the cones their rugose or wrinkled 
aspect. 
A transversal or longitudinal section shows that these 
groups, pressed one against the other, cover the whole surface 
of the cone, and that each group is formed of a little elevation 
upon which the epithelial cells are found. 
Examining one of these groups with an ordinary magnifying 
power (Yerick, obj. 6) we see that the space between the 
annular muscular fibres and the epithelial cells is occupied by 
a reticulum of connective tissue which unites the two above- 
named elements. 
The epithelial cells (fig. 13,/) are elongated, nearly cylindrical, 
but wider towards their lower part. They are separated from 
one another at their higher part, and end at their free extre- 
mity in a button-like enlargement. 
The cellular contents (A) have nearly the form of the cell. 
At the lower part the contents have the form of a club, the 
big end of which would be turned towards the bottom ; at 
the higher part the contents fill exactly the terminal enlarge- 
ment. 
This cellular substance is finely granular, but does not com- 
prise any nucleus. 
The cellular membrane is rather thick and presents, in its 
