62 FISH—CULTURAL ASSOCIATION. 
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membrane such as must be cast off in the act of hatching in the 
former cases. As soon as it has ceased to rove about in the 
water and has fastened itself to some other fixed object, it has 
attained the age of aevelopment known to oystermen by the 
term.‘ spat: 
Our researches (see Maryland Report, 1881), show that the 
dimensions of the fry of the American oyster at the time of its 
affixation when it becomes “spat” is about one-eightieth of an 
inch, and that at that time the valves are characterized by a very 
remarkable symmetry, which is departed from as soon as the 
growth of the shell begins in its new fixed position. The man- 
ner in which the fry affixes itself to foreign objects has not been 
learned, but it is very probable that this is accomplished by means 
of a larvel byssus. Such a conclusion seems to be warranted 
from the fact that the young of most of the allies of the oyster 
are provided with a byssus or threads for their temporary an- 
chorage, such as may be seen very strongly developed in the 
adult salt-water mussel, the numerous threads in this case being 
very strong, serving to hold the animal very firmly to any sup- 
port it may have chosen. 
All theorizing as to the mode of affixation aside, however, it 
now becomes a question of the most profound importance for us 
to endeavor by experiments to maintain artificially impregnated 
oyster eggs alive fora long enough time after they begin to 
swim so that they may attach themselves permanently. The ex- 
periments of those who have hitherto worked upon the devel- 
opment of the oyster have shown us that this does not yet appear 
possible. Various forms of apparatus have been tried with indiffer- 
ent success. The experiment of using bibulous paper diaphragms 
through which sea-water was allowed to pass, at the same time 
not allowing the minute eggs of the oyster to escape with the 
former, was not found to answer; the pores of the paper soon 
became clogged with fine sediment so as to stop the flow of 
water and its renewal over the eggs. Bolting cloth does not 
have the meshes fine enough to confine the eggs, besides it 1s 
expensive and not durable. The use of a membrane of filtering 
paper between single thicknesses of fine nickel-plated wire 
cloth, forming the bottom of the hatching-box, which is placed 
