373 



were followed to the closure of the blastopore. The embryos were shorter 

 than normals. 



Tautoga onitis, female. 



X 

 Menidia notata. male. 



In this cross GO per cent, of the eggs were impregnated. Some dispermy 

 and polyspermy occurred. There was a heavy mortality at the germ ring 

 stage and subsequently. The ring spread about two-thirds over the yolk 

 in some of them, when owing probably to bad conditions, all died. 



Fundulus diaphamis, female. 



X 

 E'upomotis gihbosus, male. 



The cross between the fresh water Fundulus and Eupomotis is from the 

 standpoint of impregnation, much more successful than when the egg of 

 Fundulus heteroclitus is used. The percentage of eggs fertilized may be 

 as high as 70 per cent. 



Experiment 12 56 per cent. 



17a 11 " " 



18b 70 " " 



22a 23" " 



I have always found a considerable number of imperfect eggs which 

 accounts in a measure for the usual low per cent, of eggs fertilized. A par- 

 ticularly large number occurred in Example 17a. A few of the eggs are 

 polyspermic in each experiment, probably, however, not many moi"e than in 

 the normals, where there may be as many as 5 per cent, polyspermic. The 

 development stops when the protoplasm has spread about one-half over 

 the yolk. Embryonic ring and shield are formed, but very little evidence of 

 embryonic differentiation being shown in the shield. The protoplasm looks 

 granular and opaque instead of clear, as in the normals. 



Opsanus tun, female, 



X 

 Finidiilii.'^ heteroclitus, male. 



In the one experiment made, twenty-one out of thirty-seven eggs were 

 found in the 2 and 4-celled stage eight hours and twenty-five minutes after 

 fertilization. A few of the eggs were i)oly8permic. They were followed to 

 later cleavage. 



