PORIFERA, CQHLENTERATA, VERTEBRATA 81 
Zygote 
Archeocytes 
Cells of dermal and 
gastral layers 
Tokocytes 
(Reproductive cells) 
Amebocytes 
Gonocytes 
(Sexual cells) 
Statocytes 
(Gemmule cells) 
Spermatozoon 
Zygote 
Fic. 28.— Diagram illustrating the probable history of the germ cells 
in sponges from one generation to the next. 
G 
