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. 



I 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 larv< r e 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 hoine, 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 

 larv* 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 animals, 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 holothurian or sea-cucumber 



