NATIONAL FISHERY CONGRESS. 243 
contain numbers of larvae. These were collected in the same way, the sponges being 
thrown overboard. 
It would seem in the case of sponges, as in so many marine animals, that the 
stimuli arising from confinement in a 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. 
1 have no doubt that if the sponge were handled carefully, it would be possible to 
get from the same individual, day after day during the breeding season, numbers of 
larvae, precisely as several batches of eggs are got from one codfish, for example. 
The swimming larvrn 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 cir- 
culating pipe water of aquaria, even large and elaborate ones such as those at Naples 
and Woods Hole, has been found to be unsatisfactory for the rearing of young sponges, 
as indeed it is for the young stages of many marine organisms. 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 environ- 
ment. It will probably be much better, after the attachment of the spat to pieces of 
wood, shells, etc., at once to transfer the latter to some natural site known to be 
adapted to the growth of sponges. 
I hardly think that the method of getting young sponges which I have just 
described can ever be adapted to the needs of the sponge- grower. And yet, for the 
purposes 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 koine, though at some con- 
venient depth, and in which the discharge of larvae may go on normally day after day. 
Such a box must have fine metal gauze windows on the sides and above, through which 
the water may pass freely, and yet with meshes sufficiently fine at any rate to hinder 
the passage of the larvae through them. Projecting shelves, which must be easily 
removable, might be arranged one above the other. The sides and bottom of the 
box should, moreover, be covered with removable pieces — tiles, for instance. The 
larvae settling down on the removable shelves or other pieces would attach to them, 
and might from time to time be taken out with as much ease as the honey stored up in 
the modern manufactured comb is removed from the hive. 
The precise form of live-box to be used will naturally only be determined after 
proper experiments. To prevent as far as possible the settling of the larvae on the 
body of the mother, a phenomenon very apt to occur, it will perhaps be found well 
to place the adult on a perforated tray near the top of the box, and a series of such 
trays, one above the other, may be found a good device. In planning experimental 
boxes of this sort, the character of the motion of the sponge larva should be borne in 
mind. The larva not only swims, frequently making long, shallow dives, but also 
creeps about over the sides and bottom of the vessel in which it is kept. 
The live-box has proved itself of great use to the naturalist desirous of obtaining 
the young stages of auimals, which are difficult to keep or breed in the laboratory. In 
this connection I well remember the experiences of a companion (Prof. C. L. Edwards), 
engaged in the study of the development of the large holotliurian or sea-cucumber 
