ELISHA MITCHELL SCIENTIFIC SOCIETY ne 
has the appearance of aminute incrustation. The circu- 
lar outline of the disk is soon lost, the little sponge | 
spreading in an irregular fashion over the surface to 
which it is now firmly attached. In two or three days 
the metamorphosis is complete, and we have a sponge, 
very small to be sure, and without reproductive elements, 
but like the adult in fundamental structure. Its surface 
is perforated by minute apertures, the pores, through 
which the water enters the body, and by a few larger 
apertures, the oscula, through which the water leaves 
the body. Ramifying through the interior is a system 
of spaces or canals which connect the pores with the-oscula, 
Portions of this canalsystem form spheroidal chambers, 
the walls of which are studded with cilia. It is owing to 
the motion of these internal unseen cilia that a current of. 
water is constantly circulating through the sponge body, 
carrying to its tissues the oxygen and food (minute 
particles of animal and vegetable organisms) necessary 
for their life. 
How long it takes for a sponge developed in this way 
to reach adult size and begin breeding is unknown. I 
have kept youne sponges that have transformed and 
attached: to the walls of mv laboratery aquaria for days 
and weeks. Afterthe first few days the increase in size 
has generally been imperceptible. But the unfavorable 
conditions incidental to such an unnatural habitat were 
doubtless responsible for this lack of success. 
PRACTICAL SUGGESTIONS ON REARING SPONGES 
More species of sponges breed during the warm season 
than at other times. Yet in the Mediterranean (Naples) 
some sponges are found breeding at all times of the year. 
In the Bahama Islands and on our own coast, I have found 
the breeding time of many sponges to fall within the 
period from midsummer on through early autumn. For 
