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BULLETIN OF THE BUREAU OF FISHERIES. 
The early encystment stage is one characterized by a marked transformation 
and subsequent degeneration in character, function, and appearance of the mantle 
cells. 
By virtue of the large hooks the glochidia have little difficulty in securing at- 
tachment to the fin or body proper, inclosing in this way a considerable portion 
of host tissue, the fold extending into the mantle space consisting of epidermis, 
dermis, and connective tissue; and it is from this inclosed tissue that the newly 
attached larva gets its first nourishment. This tissue breaks down into its constitu- 
ent elements by a combined process of disintegration and possible digestion, the 
latter by virtue of the supposed digestive action of the secretions of the mantle 
cells. These mantle cells as seen in preparations closely envelop the host tissue and 
would thus be enabled to pour the digestive juices directly upon the epidermis 
cells. Examinations of early stages of encystment of Anodonta corpulenta have 
shown that the so-called zymogen granules are lost shortly after encystment be- 
gins, which indicates thatr the secretory action would begin as soon as attachment 
is made and last but a short time. 
Coincident with attachment, the process of cell disintergration of inclosed 
fish tissue takes place very rapidly. Apparently the secretions of the mantle cells 
are sufficient to start the breaking down of the intercellular elements, with the 
results that the mantle cavity soon contains a quantity of broken-down cells, 
epidermis, connective tissue, red blood cells, leucocytes, and cellular detritus. 
Even though there at times is a noticeable hyperplasia of the tissue at the base of 
the cyst during early formation, red blood cells being especially noticeable, it is 
doubtful if there is ever an appreciable migration of leucocytes between the valves 
and, whenever it does occur, it probably represents a pathological condition detri- 
mental to the mussel. Faussek records a phagocytic reaction of the leucocytes 
against encysted mussels that is a specific cause for death, and the author has 
evidence of a similar mortality of Lampsilis luteola occasioned in the same way. 
However, the author is of the opinion that the larval mussel is normally resistant 
to leucocytes, and, when phagocytosis occurs, it represents a condition of suscep- 
tibility of the mussel occasioned in some unexplainable manner, possibly associated 
with mantle cell reactions, or perhaps in a larger sense with possible immunity 
reactions between host fish and its mussel parasite. 
INGESTION OF FOOD. 
The mantle cells in the meantime have lost their original character and ap- 
pearance. The so-called zymogen granules, which were such conspicuous elements 
of the glochidial mantle cells in stained preparations, are no longer in evidence, 
and there is a probable transformation from a secretory to an ingestive function, 
the mantle cells becoming looser in texture, somewhat vacuolated, and character- 
ized by a tendency toward pseudopodial formation by which the broken-down cell 
matter is ingested and taken to the interior (fig. 3), so that nutrition becomes an 
intracellular process. Stained material at this stage shows the mantle cells contain- 
ing an abundance of disintegrated cells, the nuclei of which are readily distinguished 
from those of the mantle cells, since the nuclei of the latter, along with the transi- 
