26 BULLETIN OF THE BUREAU OF FISHERIES. 



the small simple masses finally produced in the two forms. In Slylotella these bodies 

 are aggregations of syncytial protoplasm quite without cell boundaries, and studded 

 with nuclei that are optically all alike. In the Spongillidae discrete cells can be dis- 

 tinguished in them, apparently of two kinds. Miiller finds that the reduced choano- 

 cytes are engulfed and digested by some of these cells, the granular elements. As to 

 this question, concerning the persistence or absorption of the choanocytes, I was not 

 able to reach a definite conclusion. 



It is important that Miiller was able to get one of his reduction masses to transform 

 into a sponge, and so really to prove that the tissue composing such masses is regener- 

 tive tissue and that the masses are therefore not stages in a series of purely mortuary 

 changes, the bizarre character of which, in the case of slowly d)'ing protoplasm, must 

 be familiar to many. Possibly the method I employed in handling the Stylotella masses, 

 and which permitted them to transform, whereas in laboratory aquaria they uniformly 

 refused to do so, might prove applicable to the Spongillidae. 



As Korschelt and Heider remark in the latest installment of their textbook" (p. 486) , 

 it is probable that such bodies occur widely in the sponges. The peculiar capsules 

 formed on the surface of Spongelia kept in aquaria and described as early as 1886 by 

 Thomson * are in all likelihood bodies of this kind. Thomson recognized them as such, 

 and speaks of them " as a histological modification in response to a change in the environ- 

 ment," and again "it seems possible that they may thus secure the persistence of the 

 organism in unfavorable environment." Maas {vide infra) has found them in 

 calcareous sponges. Lendenfeld mentions "^ that he has obser\'ed similar formations in 

 Reniera and Sycon. Urban "^ has recently studied their origin in the Calcarea (Clath- 

 rinidae). Miiller raises the question whether it is proper to designate these bodies as 

 "artificial gemmules." I agree with him in finding the terminology unsatisfactory. It 

 draws attention away from the fact that what is formed is a tissue, a simplified, regenera- 

 tive tissue. This may take the shape of small spheroidal masses scattered through the 

 interior of the old sponge, in which case the resemblance to the gemmules of the Spongil- 

 lidae, or better, to such simpler ones as are formed in the Chalinidae, is marked. But 

 identically the same tissue may collect in masses scattered over the general surface of 

 the sponge. And here, while some of them may be spheroidal and small, usually they are 

 flattened and of an irregular shape with lobes, suggesting a lobose rhizopod or myxomy- 

 cete Plasmodium.* There are no facts which indicate that such masses regularly sub- 

 divide into small spheroidal bodies. Thus in the one case the regenerative tissue 

 collects to form masses, the size and shape of which vary greatly, probably being deter- 

 mined by local conditions, while in the other case, in the Spongillidffi, a reproductive 



o Korschelt und Heider: Lehrbuch der vergleichenden Entwicklungsgeschichte der wirbellosen Thiere. Allgemeiner Theil, 

 4te. lief., 2te. hfte., 1910. 



b Thomson. J. Arthur: On the structure of Suberites domuncula, Olivi (O. S.). together with a note on peculiar capsules found 

 on the surface of Spongelia. Tiunsactions Royal Society of Edinburgh, vol. xxxra, pt. i. 



*■ Lendenfeld, R. von: Zoologisches Centralblatt.. bd. 14. 1907. p. 631. 



'^ Urban, F.: Zur Kenntnis der Biologic und Cytologic der Kalkschwamme (fam. Clathrinidjp Minch.). Internationale 

 Revue der gesamten Hydrobiologie und Hydrogaphie, bd. 3. 1910. 



« Wilson. H. v.: A new method by which sponges may be artificially reared. Science, n. s.. vol. xxv, June 7, 1907. 



