406 EDITH PINNEY 



we have a cross in which this block to normal mitosis of the ana- 

 phase period is absent. Figures 9 and 10 are from my material 

 and present first and third cleavage conditions during the criti- 

 cal period. Division is normal. 



4. Fundulus heteroclitus 9 X Stenotomus chrysops cf 



Of this cross I am able to give only second-cleavage figures 

 (11, a and b, and 12, a and b). These show the usual condi- 

 tions in straight-fertilized eggs. There is no lagging or clumping, 

 and I feel that one may safely conclude that the same conditions 

 prevail during the first cleavage. I base this inference upon 

 observations made on other crosses reported here and else- 

 where (15). 



Figure 12 shows the two sections of one spindle. The chromo- 

 somes were so well separated that it was possible to count them. 

 There are forty-six at either pole. In figure 11a the individual 

 chromosomes have been drawn spread out laterally, so that all 

 of the rods of each group are not reproduced in their actual posi- 

 tions. Such a drawing illustrates how much more can be gained 

 from a study of the preparations than is indicated by the drawings 

 themselves. In this figure the longer Fundulus chromosomes 

 are easily identified, as are the smaller Stenotomus elements. 

 The rods of medium length cannot with certainty be ascribed 

 to either species. There is a definite grouping on this second- 

 cleavage spindle. Evidently, the plane of the section has passed 

 to one side of the Fundulus group, as all of the long rods are in 

 one section. The smaller chromosomes in figure 12 b belong to 

 the Stenotomus group. 



This cross, therefore, shows the type of behavior that is char- 

 acteristic of self-fertilized eggs. It falls in the same group as 

 the cross with Menidia. 



II. RECIPROCAL CROSSES BETWEEN CTENOLABRUS ADSPERSUS 

 AND PRION OTUS CAROLINUS 



In all of the reciprocal crosses with the cunner which I had 

 studied up to this time there was a marked difference in the 

 chromatin behavior during the early anaphases. In the crosses 



