212 
BULLETIN OF THE BUREAU OF FISHERIES. 
degree of development is usually less with the hookless glochidium. The endoderm 
has the same prominence, as have the lateral pits of the mesoderm. The larval 
mantle cells have the same relation to the underlying tissues, with a break in con- 
tinuity in the region just posterior to the adductor, leaving this area uncovered. 
One would expect, then, to find a similar development with such relatively close 
histological uniformity. 
FIRST ENCYSTMENT STAGE OF LAMPSILIS LUTEOI.A. 
On implantation one observes the same coordination of functions as have been 
discussed with the hooked type. For a short time after attachment, for a period 
of a couple of hours at least, the supposed secretory function predominates and 
sections, as Figure 5, show the mantle cells still retaining their original appearance. 
They are remarkable for their compactness; they 
have a very firm, almost a hard texture in view 
of the excessive refractive granulation; the nuclei 
are small, the nucleoli are not prominent, and 
the individual mantle cells are flat, rather than 
cylindrical. Cell boundaries, as with the Ano- 
dontas, are very indistinct, so that the mantle 
appears to be a homogenous nucleated structure. 
Disintegration of the inclosed tissue is observable 
at this time, so that the mantle space contains a 
quantity of cellular debris, although there is no 
evidence' of mantle cell transformation at this 
time. With the close of the supposed secretory 
function of the Anodonta glochidium there is in- 
itiated the series of degenerative changes that 
result in the formation of the “mushroom body.” 
With the loss of granulation the cells of the man- 
tle of Lampsilis luteola, instead of fusing, merely 
lose their granulation, and the cell boundaries, 
become more distinct. The free inner surfaces 
project into the mantle cavity as individual cell areas; there is the appearance of 
the pseudopodial character and the intracellular ingestion of the disintegrated 
host cells. Because of the retention of individualism the mantle cells project more 
into the mantle cavity and envelop the fold of fish tissue more closely than does 
the fused mantle of the Anodontas, which takes on somewhat of a blanket structure, 
with short pseudopodial processes, so that there can be no individual extension 
of whole cells as with luteola. 
As ingestion of cell material is initiated the large mantle cells undergo a marked 
increase in size, and there is undoubtedly a storing up of food matter through the 
conversion of the ingested food cells. In the Anodontas the mantle early takes 
on a vacuolate structure, which becomes pronounced as degeneration progresses, 
and there is the rapid transformation in the character of the nuclei, which become 
distended, with the nucleoli conspicuous. Kelative to intracellular nutrition of 
Fig. 5. — Encysted glochidium of L. luteola li 
hours after attachment, showing retention of 
original granular nature of larval mantle cells. 
The pseudopodial nature has not become evi- 
dent. 
instead of becoming obscured, 
