ELISHA MITCHELL SCIENTIFIC SOCIETY 80 
It would seem in the case of sponges, as with so many 
marine animals,that the stimuli arising from confienment 
ina limited volume of water lead to the rather sudden 
discharge of those embryos (or in certain forms, eggs) 
that have reached the proper stage for birth. 
I have no doubt that if the sponge were handled care- 
fully, it would be possible to get from the same individual, 
day after day dnring the breeding season, numbers of 
larvae, precisely as several batches of eggs are got from 
one codfish, for example. 
The swimming larvae thus obtained may be made to 
attach, during the next day or two, to the walls of the 
dishes in which they are kept, or to pieces of wood or 
small stones. After attachment the young, or, as we 
might say, the sponge ‘‘spat,’’ are easy to handle, In 
this connection, however, it will be well to bear in mind 
that the circulating pipe water of aquaria, even large 
and elaborate ones such as those at Naples and Woods 
Holl, has been found to be unsatisfactory for the rearing 
of young sponges, as indeed it is forthe young stages of 
many marine organism. The sponges become covered 
with sediment, and bacteria develop. Changing the 
water in the dishes twice a day is, on the whole, a better 
method. But this is far from an ideal environment. It 
will probably be much better, after the attachment of 
the spat to pieces, of wood,shells,etc., at once to transfer 
the latter tosome natural site own to be adapted to the 
growth of sponges. 
I hardly think the method of getting young sponges 
which I have just described can ever be adaptedto 
the needs of the sponge-grower. And yet for the pur- 
poses of experiment, where a few hundreds or a thousand 
young sponges would suffice, the method is adequate. I 
believe, however, that live-boxes may be devised in which 
the sponge may be kept imprisoned in its natural home, 
