914 



SCIENCE 



[N. S. Vol. XXV. No. 649 



inclusions and is reticulate in arrangement. 

 The nuclei are practically all alike, and there 

 are no signs of persisting collar-cells. Such 

 a mass represents a portion of the original 

 sponge in which the degenerative changes have 

 progressed farther than in the larger rem- 

 nants. In the latter we find a syncytium 

 made up of discrete cells among which some 

 persisting collar-cells are distinguishable. But 

 in the plasmodial mass the cells have united 

 80 intimately that cell outlines have been 

 wiped out, and recognizable collar-cells (or 

 their nuclei) have disappeared. The optical 

 evidence points to the conclusion that the lat- 

 ter help to form the general syncytium, under- 

 going regressive changes in their differentia- 

 tion which result in their becoming indifferent 

 parts of this unspecialized tissue. 



The plasmodial masses remain alive in the 

 laboratory indefinitely, but do not transform. 

 They attach to the bottom of the vessel, but 

 so feebly as to be easily shaken loose. In 

 order to see if they would transform when 

 returned to natural conditions, I devised the 

 simple plan of enclosing them in fine bolting- 

 cloth bags which were hung in a live-box float- 

 ing in the harbor. The bags, rectangular, 

 were divided into compartments about an inch 

 square with the two flat sides nearly touching. 

 In each such space an isolated plasmodial mass 

 was inserted, and the bag sewed up. It was 

 found that in such bags the masses were held 

 in place long enough for them firmly to attach 

 to the bolting cloth. Once attached to the 

 cloth they grow, sometimes quite through the 

 wall of the bag to the outer water, and trans- 

 form into perfect sponges with osculum, can- 

 als, pores and flagellated chambers in such 

 abundance as to be crowded. 



This ability to undergo — when the environ- 

 ment is unfavorable but not excessively so, 

 regressive changes of differentiation resulting 

 in the production of a simpler, more uniform 

 tissue, is something that is plainly useful, i. e., 

 adaptive. In the simplified state the sponge 

 protoplasm withstands conditions fatal to such 

 parts of the body as do not succeed in passing 

 into this state, and on the return of normal 

 conditions again develops the characteristic 

 structure and habits of the species. That this 



power is exercised in nature there can scarcely 

 be a doubt, since the conditions that are pres- 

 ent in an aquarium must now and then occur 

 in tidepools. 



It is probable that the power thus to degen- 

 erate with production of masses of regenerar 

 tive tissue is general among sponges. I first 

 discovered the phenomenon in Microciona, a 

 very different form from Stylotella and one in 

 which the skeleton includes much homy mat- 

 ter. And in two other Beaufort species I 

 have succeeded in producing the plasmodial 

 masses. . There is every reason for believing 

 that the commercial sponge shares in this 

 ability. If this is so, we have here a means 

 of propagation which with a further develop- 

 ment of methods may at some time become 

 economically practicable. In any case it is 

 now possible to study the differentiation of a 

 quite unspecialized tissue, one that is physi- 

 ologically embryonic, into a perfect sponge at 

 any time of the year irrespective of the breed- 

 ing season. We may even exercise some 

 direct control over the size of the plasmodial 

 masses, as the following experiment shows. 



Microciona was kept in aquaria until the 

 degenerative process had begun. Pieces were 

 then teased with needles in a watch glass of 

 sea water in such a way as to liberate quanti- 

 ties of cells and small irregular cell-agglomer- 

 ates. These were gently forced with pipette 

 to the center of the watch glass. Fusion of 

 cells and masses, with amoeboid phenomena, 

 began at once, and in half an hour quite large 

 irregular masses existed. In the course of a 

 few hours the masses grew enormously through 

 continued fusion. From this time on they ad- 

 hered fijmly to the glass, retaining irregular 

 plasmodium-like shapes, and the growth was 

 inconspicuous. To bring them together once 

 more and induce further fusion they were on 

 the following day forcibly freed, with pipette 

 and needle, and to clean them of cellular 

 debris and bacteria were transferred to a 

 tumbler (covered with bolting cloth) in which 

 they were kept actively moving under a fine 

 glass faucet for about thirty minutes. In the 

 course of this violent agitation a good many 

 masses were lost. Those remaining in the 

 tumbler became in the next few hours notice- 



