216 
BULLETIN OF THE BUREAU OF FISHERIES. 
tissue. With, the mushroom body of Anodonta there is a constant utilization and 
resorption, being a drain on its protoplasmic resources by the remainder of the 
organism, giving it its analogy to a fasting or starved cell, especially so during the 
latter stages of encystment, so that the lack of staining ability is readily understood. 
So, in this case, with the mushroom body, we have lack of staining associated with 
degenerative changes. 
With Anodonta, regeneration of the mantle is complete by the end of parasitism, 
the mushroom body disappearing and the definitive mantle attaining its complete 
development, so that when liberation occurs the tissue transformation has been 
complete. 
The development of the definitive mantle progresses more slowly in luteola, 
the larval mantle cells being in evidence at the time the mussel is shed by the fish. 
The final completion of the definitive mantle takes place very quickly, however, 
and many specimens collected two days after shedding showed the definitive mantle 
in an almost complete condition (fig. 11). Many of these individuals still possessed 
the larval mantle cells, which were interesting in that they were not extended, as 
during encystment (fig. 8), but were contracted, with the pseudopodial processes 
very evident. Whether or not there could have been any ingestion of food by these 
mantle cells by virtue of their pseudopodia is a matter of question. Granules were 
seen in many of these cells, but their nature could not be determined. 
In view of the rapidity with which the completion of the definitive mantle 
takes place, it is only to be expected that whenever retention on the fish is prolonged 
the final transformation of the mantle takes place during parasitism instead of 
following it. 
No indication has oeen seen so far of atrophy of these larval mantle cells as the 
means whereby their final disposal takes place. With free mussels the throwing 
off of these cells is shown in Figure 12. Here there is a very obvious disintegration. 
Fig. 12.— Transverse horizontal sec- 
tion through mantle cells of devel- 
oped free larval mussels of L. lu- 
teola, showing nature of shedding 
of larval mantle cells, d. m. c., 
definitive mantle cells; l. m. c., lar- 
val mantle cells; vac., vacuoles. 
Fig. 10.— Developed free larval mus- 
sel of X. luteola, hut with larval 
mantle cells still present. Sym- 
bols same as Fig. 7. 
Fig. 11.— Developed free larval mussel 
of X. luteola, with larval mantle cells 
replaced by definitive mantle, d.m. 
c., definitive mantle cells; m. s., 
mantle sinus. 
