66 FISH—CULTURAL ASSOCIATION. 
covered slates are used will be a particle more likely to afford a 
nidus for spat than old shells, or the cheapest kind of cultch, 
except in some places where the latter is liable to be covered 
with mud or sediment. 
This uncertainty of result can, it appears to the writer, be 
overcome by a totally different method of procedure, like that 
already outlined. We must have the temperature of the water 
and conditions of the artificially fertilized and confined embryos 
under control. The uncertainty which has hitherto attended 
ostraculture must disappear in the face of intelligent experi- 
ment, and it isto be hoped that in a few years more we will 
hear of oyster nurseries or incubating establishments in success- 
ful operation where millions of spat will be annually bred from 
artificially impregnated eggs to be sold as seed to planters who 
will enter upon the business of ostraculture on an entirely new 
and scientific basis. 
Of no less moment than the introduction of radically new and 
more certain methods of propagation, is the question, “ Upon 
what does the oyster feed ?” and, what are the conditions of life 
which will most quickly bring the animal into a plump, market- 
able state? The most contradictory and confusing statements 
are made by different persons in regard to the feeding habits of 
the animal, and anomalous as some of them may at first appear, 
many of them doubtless have some foundation in substantial 
fact. | 
Prof. Leidy, at a recent meeting of the Academy of Natural 
Sciences of Philadelphia, stated it as his belief that oysters feed 
at times on the zoospores of certain algz, as those of Ulva latis- 
sima (sea cabbage), which he knew from personal observation to 
be green, and which he thought might possibly be the cause of 
the green coloration of the soft parts of the animal as sometimes 
observed in certain localities. Very possibly this may be the 
case, but judging from what I have seen and heard from oyster- 
men, as well as from what I have read in various publications 
relating to this matter, I am not inclined to regard this as the 
only source of the unusual green tint of the flesh of the oyster. 
I hope to be able to show that it is probably of vegetable origin, 
and therefore quite harmless. That it is not copper we may be 
