IQlJf.'] Abstkacts and Keviews 119 



sponges and calcareous sponges. Karl Muller^ has succeeded in 

 growing Spongillas from dissociated cells. And Julian S. Hux- 

 ley,^ working at I^aples, also succeeded in developing Sycon 

 raplianus in tlie same way. 



W. C. George. 



ON THE BEHAVIOR OF THE DISSOCIATED CELLS IN HYDROIDS 



In this paper^ Dr. H. V. Wilson shows that hydroids may like- 

 wise be grown from dissociated cells. The methods practiced were 

 essentially the same as those used for sponges. The hydroids, 

 however, proved far more difficult objects to handle. Neverthe- 

 less, hydropolypes (Eudendrium, Pennaria) were developed 

 with the characteristics of the species. Here again the methods 

 may prove of use in studies of the origin of sex. In this paper 

 Professor Wilson considers his observations more directly than 

 in preceding papers from the standpoint of the reduction theory. 

 He points out that in sponges this question is complicated by 

 the presence in the sponges of large numbers of undifferentiated 

 cells (amoebocytes). But in hydroids, such cells are present 

 in a negligible quantity, and the restitution masses, therefore, 

 undoubtedly are derived from the differentiated ectoderm and 

 entoderm cells. These cells after dissociation lose their dis- 

 tinctive histological characteristics and combine to form a solid 

 mass which again differentiates like a coelenterate embryo into 

 ectoderm, entoderm, and a central yolk. These facts then cer- 

 tainly lend great weight to the idea that differentiated somatic 

 cells may undergo a process of regressive differentiation (re- 

 duction), and pass into a generalized state physiologically sim- 

 ilar to embryonic tissue. 



W. O. George. 



'^ Das Rec/encrationsvermoffen der Suswasserschwamme, insbesondere Unter- 

 siichinif/cn iiher die hel iluien vorkommende Regeneration nacli Dissociation und 

 Reunition. Archiv P. Entwicklungsmechanik der Organismen, 32: 397-446. 1911. 



^ Some Phenomena of Regeneration in Sycon; xcith a Note on the Structure 

 of Its Collar-cells. Philosophical Transactions of the Royal Society of London. 

 Series B, 202 : 165-189. 1911. 



3 The Journal of Experimental Zoology 11 : 281-338. 1911. 



