246 EDITH PINNEY 



is a constant feature of this cross is uncertain. Another lot of 

 eggs of the same cross, killed in the four-celled stage, shows very 

 few vacuoles. At a much later stage, in still another lot of eggs, 

 only occasional vacuoles appear. 



Figures 53 is drawn from a section through a later hybrid 

 blastoderm and shows the latest stage offered by the material 

 studied. The mitotic figures are quite normal. Figure 54 is a 

 polar view of an anaphase plate found in an egg of this stage. 

 Forty- two chromosomes are present. 



Some abnormal mitotic figures were present in eggs which 

 showed very irregular cleavage and which were probably poly- 

 spermic eggs. A few instances were noted in which solid black 

 deposits of the same nature as that shown at A, figure 53, but 

 much more extensive, were present at the periphery of the egg. 

 This deposit sometimes fills an entire cell. In some cells it 

 occupies the region of the aster and occasionally a lagging mitosis 

 is found near the affected region. In this case the abnormal 

 cell division is caused by the peripheral disturbance, the nature 

 of which is not understood. 



A large number of the eggs of this experiment developed nor- 

 mally up to the time of hatching, but none were able to hatch. 

 Superficially they resembled pure Ctenolabrus embryos. New- 

 man has obtained many hatching embryos of the maternal type 

 from this cross. 



Stenotomus chrysops 9 X Ctenolabrus adspersus cf 



While the cross just described is one of the most successful 

 of the heterogeneous crosses thus far made, in that it has been 

 carried through to hatching, the reciprocal cross, Stenotomus 

 chrysops 9 X Ctenolabrus adspersus cf , has never been reared 

 beyond the gastrulation stages. For that reason the abnormali- 

 ties found in the behavior of the chromosomes in this cross are 

 especially significant. The material studied was obtained from 

 three experiments, and the same irregularities are found in all 

 lots. 



In this cross, as in the previous one, the only evidence that the 

 chromosomes appearing in the cleavage mitoses comprise the 



