CHROMATIN — DEVELOPMENT AND HEREDITY 251 



Figures 76 to 78 are from eggs which had developed for two 

 hours and forty-six minutes. • The mitotic figures are still of 

 good size and the familiar rods, hooks and V's are easily made 

 cut. Since the chromosomes are crowded into less space than 

 in the earlier cleavages, all of the elements of an anaphase plate 

 could not be drawn with the camera. Consequently, these 

 lateral views give no idea of the chromosomal number character- 

 istic of the hybrids. This is shown in figure 79, which is a polar 

 view of an anaphase plate. Forty-one chromosomes are counted. 



All of the material from this cross, with, of course, the exception 

 of polyspermic eggs, exhibits normal chromosomal behavior. 

 In view of the character of the early cleavages, the irregularly 

 divided blastoderms which occur frequently in the later material 

 may be regarded as originating from polyspermic eggs. In these, 

 multipolar mitotic figures occur. These of course show lagging 

 chromosomes, but in the bipolar figures of the same eggs the 

 division of the chromosomes and their migration to the poles 

 take place in the normal manner. 



Newman reports this cross among those which do not survive 

 gastrulation. In nij experiments some of the embryos remained 

 alive for nearly three days. None hatched. All were ab- 

 normal, but no close examination was made to determine the 

 nature of the defects. 



Attention has already been called to the fact that in the cross 

 Ctenolabrus 9 X Fundulus cf the production of more chromatin 

 by the Ctenolabrus egg is demanded than in normally fertilized 

 eggs. This led to the idea that a possible disturbance of the 

 metabolic processes concerned in the production of chromatin 

 caused the early death of these eggs. In this case, Ctenolabrus 

 9 X Menidia d^, the amount of chromatin necessary for the 

 regular development of the paternal chromosomes is not appreci- 

 ably greater than in the pure Ctenolabrus egg, since the Menidia 

 chromosomes are of about the same dimensions as those of 

 Ctenolabrus. Their combined bulk may even be less. 



