112 GEORGE LEFEVRE AND WINTERTON C. CURTIS 
varying in amount with the extent of the "bite/' becomes en- 
closed within the mantle space of the glochidium. This tissue 
early disintegrates into its cellular constituents, which are taken 
up by the pseudopodial processes ol the larval mantle cells, and 
as Fausek ('95) has described, are utihzed as food during the early 
stages of metamorphosis. In fig. 37, drawn from a glochidium 
six hours after attachment to a fin, the disintegrated tissue, con- 
sisting of loose epithelial cells, blood corpuscles, and fibers which 
lie scattered in the mantle cavity, is seen in the process of being 
ingested by the mantle cells. Fig. 38 shows a later stage, twenty- 
four hours after attachment, in which the detritus has been en- 
tirely taken up, and the mantle cells are now heavily charged with 
food material. 
Almost immediately after attachment proliferation of the epi- 
thelium begins as the initial step in the formation of the cyst which 
eventually encloses the entire glochidium. The overgrowth of 
the larva has been described by Fausek ('95) and Harms ('07, '09) 
as a healing process on the part of the fish's tissues, resulting from 
the irritation caused by the wound. The proliferation starts 
around the line of constriction produced by the pressure of the 
edges of the valves on the epithelium, and, since the glochidium 
lies between and prevents the immediate closure of the lips of 
the wound, the extending epithelium is forced to slide up over the 
surface of the shell on all sides, until the free margins meet and 
fuse over the back of the larva, as may be understood by refer- 
ence to figs. 15-18 and 20-22. 
So rapid is the overgrowth, especially in the case of implanta- 
tion on the gills, that it would seem that something more than the 
mere mechanical irritation produced by the glochidium is con- 
cerned in causing the proliferation of the epithelium. We have, 
therefore, carried out a series of experiments with a view to de- 
termining whether or not, a chemical stimulus is provided by the 
larva, and by using various methods have studied the action of 
glochidial extracts on the epithelium of both fins and gills. The 
results have been entirely negative, although the question has 
by no means been settled by the experiments which have been 
thus far attempted. By further improvements in the technique. 
