SIGNIFICANCE OF LARVAL MANTLE OF FRESH-WATER MUSSELS. 
215 
considerable development and is readily recognizable, standing out very sharply 
from the rest of the tissue because of the uniformity of its short cylindrical cells. 
These definitive mantle cells take the form of a pyramid structure, giving rise to 
the internal mantle sinus, which is an important part of the lymphatic system. 
It is difficult to know what interpretation to place on obvious nutritional 
organs. With the Anodontas it is assumed that the nutritional function is carried 
by the definitive mantle, since the larval mantle is being absorbed at this time. 
With luteola, of which the larval mantle cells retain a uniform condition and appear- 
ance throughout the entire period of parasitism, it seems only fair to assume that 
as they have a nutritional function during the beginning of the parasitic period 
they have the same r61e at the close of parasitism, their appearance remaining the 
-d.mc. 
Fig 
—View similar to Fig. 2, but more enlarged. 
m. s., mantle sinus. Other symbols same as in Figs. 
6 and 7. The red blood cells in host tissue clearly 
shown. 
Fig. 9. — Enlarged view of mushroom body of A. corpulenta, 
with the vacuolate character in evidence. The high cylin- 
drical cells of the definitive mantle are well shown. 
same. With this the case, we have nutrition being taken care of by both the larval 
and the definitive mantle cells, and this at the present time seems to be the only 
interpretation that can be given. 
One noticeable characteristic of the larval mantles of both Anodonta corpulenta 
and Lampsilis luteola is their almost negative staining reaction to eosine. Even 
heavy exposures to this stain during the end of the parasitic period fail to take, 
and the mushroom body of corpulenta and the individual mantle cells of luteola 
are always remarkable for their transparency in stained preparations. Churchill 
(1916) alludes in his work to the lack of staining capacity of fasting or starved cells, 
using this as a basis for determining the presence of epithelial food absorption. 
He found that starved cells took a very much lighter eosine stain than normal 
