FACTORS IN OXTOGEKY 



277 



G 



Fig. 157. — A, Hybrid larva {Sphrcr echinus ? and Echinus i), front view; B, the same 

 from side view; C, hybrid larva, Spharechinus ? (nonnucleated egg formation; 

 and Echinus i , of the type; D, the same larva in side view. (After Boveri.) 



19 



