STRTJCTUBE OF THE LARVA OF SPONGILLA LAOUSTRIS. 445 



The second view to be discussed is the one which was for a 

 long time almost universally held to be the fate of the flagel- 

 lated cells in most sponges. Ganin (4) and Maas (7) are the 

 authors who have given expression to this view with regard 

 to the fate of the flagellated cells of the Spougilla larva. Further 

 comment on the view under consideration would be unneces- 

 sary, as it is practically obsolete^ had not Mr. H. V. Wilson 

 (17) given it his support as late as the year 1894 in his obser- 

 vations on the gemmule and egg development of marine 

 sponges. However, in spite of Wilson's attempt to reinstate 

 this view in its former position, all that is necessary is to point 

 out that he makes some very important admissions : first, that 

 he has never seen the flagellated cells being transformed to 

 the cells of the flat epithelium or so-called " ectoderm ; " and 

 secondly, that some of the ectoderm cells (meaning flagellated 

 cells) of the larva migrate into the interior during metamor- 

 phosis. These admissions, together with others made in 

 Wilson's account, are fatal to the view which he upholds, not 

 to speak of the fact that his figures in spite of himself tend to 

 support the opposite view. However, with regard to Spougilla 

 the only statement I wish to make is that I consider that such 

 figures as 15 a and 15 of the present paper cannot be otherwise 

 explained than as a most convincing and final proof that the 

 cells with granular nuclei pass out to form the flattened epithe- 

 lium, and that the flagellated cells pass to the interior, which 

 is the view now held by Maas (8), and from the first by Delage 

 (1) andNoldeke (13). 



Though these three authors agree as to the immigration of 

 the flagellated cells, they differ considerably as to their ultimate 

 fate. Maas and Delage, however, support the view that they 

 become the collar-cells of the young sponge, but differ widely 

 as to the details of the process of transformation. 



Maas holds that they become the collar-cells directly, and 

 without passing through any such series of changes as have 

 been described by Delage in the formation of his " polynuclear 

 groups." Maas undoubtedly saw the "polynuclear groups" 

 of Delage, the plasmodial aggregations of the present 



