PORIFERA, CCELENTERATA, VERTEBRATA 77 



undifferentiated tissue of which they are composed, 

 undoubtedly consists largely, if not entirely, of 

 amebocytes (Weltner, 1907). These amebocytes 

 are, however, of heterogeneous origin (Maas, 1910), 

 since some of them represent transformed pore 

 cells, whereas the rest are wandering cells. 



Even more interesting than these reproductive 

 bodies are the artificial plasmodia produced by Wil- 

 son (1907, 1911) in Microciona^ Lissodendoryx, and 

 Stylotella and by Muller (1911) in the Spongillidse. 

 The method and results from a study of Microciona 

 as stated by Wilson (1911) are briefly as follows. 

 Branched specimens are cut up and strained into a 

 dish of water through fine bolting cloth. The 

 cells, which are dissociated in this way, "settle 

 down on the bottom of the dish like a fine sediment." 

 Three classes of cells are present : (1) ** the most con- 

 spicuous and abundant" are unspecialized granular 

 "ameboid cells of the sponge parenchyma (amcebo- 

 cytes) " ; (2) "a great abundance of partially 

 transformed collar cells"; and (3) "more or less 

 spheroidal cells ranging from the size of the granular 

 cells down to much smaller ones." 



"Fusion of the granular cells begins imme- 

 diately and in a few minutes' time most of these 

 have united to form conglomerate masses which at 

 the surface display both blunt and elongated pseu- 

 dopodia. These masses (plasmodia) soon begin to 

 incorporate the neighboring collar and hyaline cells." 

 "The small conglomerate masses . . . early begin to 

 fuse with one another," and if the tissue is strewn 



