LEPTOMEDUSjE — OBELIA. 



251 



Weismann and de Varenne find that the germ-cells in Obelia scutulata originate in the 

 entoderm of the stem of the hydroid, and then migrate into the medusa-bud, finally pushing 

 through the entoderm into the ectoderm, which thus incases them in the free medusa.' Billardt 

 1901, finds that this hydroid often reproduces itself through scissiparity. 



"Eucope" polygena A. Agassiz, 1865, appears to be only a variety or environmental race 

 ot Obelia geniculata. 



'32. 



Fig. n o.-Obelia " fiabellata" = . plana, after Hincks, in British Hvdroid Zoophytes. 



ric. i^i.-Obeha "flabellala," after Hincks, in British Hvdroid Zoophytes. 



Fie. ijz.-OW u geniculata var. polygena, after A. Agassiz, in North American Acalephx. 



