PORIFERA, CCGELENTERATA, 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 Miiller (1911) in the Spongillide. 
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 
