Plate I 



Above Young Echinus larvae, after BOVERI (1903 a}. 



A. Larva reared from nucleated egg-fragment in which the egg nucleus 

 united with a sperm nucleus. B. Larva reared from non-nucleated egg- 

 fragment, from the same parents ; the nuclei in B are thus derived 

 from the sperm nucleus only, and are half as large and twice as 

 numerous as in A. 



Belong Stages of Amitotic division in nuclei of the Malpighian tubules of the 

 Stick-Insect Diapheromera, from MARSHALL. 



