ON THE FEASIBILITY OF RAISING SPONGES FROM THE EGG. 



BY H. V. WILSON, PH. D., 



Professor of Biology , University of North Carolina. 



For the purposes of scientific investigation the problem suggested in the title of 

 this paper presents no difficulties to the zoologist. Whether on the other hand it is 

 practicable or even desirable to rear sponges from the egg for the purposes of the 

 sponge-grower, is a question which can only be decided by experiments carried on 

 continuously for some years. From the standpoint of the scientific breeder such 

 experiments seem eminently desirable, and the probability that they would result in 

 economic discoveries of importance is very great. It is my purpose to point out 

 toward the end of this paper some of the advantages attainable, as I believe, by this 

 method of breeding. I shall preface my remarks on the rearing of sponges with a 

 brief account of the manner in which the egg development goes on. 



Some sponges are known to be hermaphrodite, others have been described as of 

 separate sexes. The probability is that sponges are in general hermaphrodite, but 

 that the individual at one period produces chiefly male elements, and later chiefly 

 female elements. Fertilization takes place in the body of the mother and the egg 

 here undergoes its early development. The embryo eventually bursts the maternal 

 tissue, and, passing into one of the canals, is caught by the current sweeping through 

 the canal system and is discharged into the surrounding water through one of the 

 large apertures (oscula) on the surface of the sponge. 



In the great majority of sponges (horny and silicious forms) the embryo, or larva 

 as it now should properly be called, since it leads a free life, is an oval, solid body, 

 covered with slender hair-like processes of protoplasm, the so-called cilia. The cilia 

 strike rhythmically to and fro, like so many minute and flexible paddles, and the 

 sponge larva is by their means whorled through the water. Sponge larvae, of course, 

 vary in size, but frequently have a length in the neighborhood of 1 mm. (^ inch). 

 The surface layer contains more or less pigment. Thus, in the commercial sponge, 

 Euspongia, the larva is whitish, with a brown spot at one end. In Tedania brucei, a large 

 red sponge, growing especially on the mangroves in parts of the Bahamas, the larva 

 is a beautiful red. 



The free-swimming life of the sponge larva is short, lasting, when bred in the 

 laboratory, only a day or two. During this period the larva is moved along not only 

 by its own relatively feeble motion, but, being subject to the action of currents, it 

 may be carried a considerable distance from the spot where it was born. It eventually 

 settles down on some firm basis and transforms. The cilia are lost, and the oval 

 body flattens out into a disk so thin that it has the appearance of a minute incrusta- 



241 

 F. C. B. 189716 



