372 



developed further since my notes, at this stage, show them to be in a good 

 condition. 



Gasterosteus hispinosus, female, 



X 

 Memdia gracilis, male. 

 In two of the three experiments made with this cross, practically 100 

 per cent, of the eggs were normally impregnated. The eggs develop at the 

 sarne rate as the normals until the latter half of gastrulation, when the 

 hybrids fall behind. Most of the eggs form embryos. These are short, with 

 heavy anterior portion. The posterior one-half or one-third of embryo 

 remains quite rudimentary. The anterior enlarged end develops eyes that in 

 the earlier stages are apparently normal. The heart is formed and pul- 

 sates. I have kept these embryos alive for five days. 



Gasterosteus Mspinosus, female, 



X 

 Tautoga onitis. male. 



Practically 100 per cent, of the eggs were normally fertilized in the 

 single cross made. The eggs show the usual slowing in development at the 

 close of segmentation. About 50 per cent, of the embryos died at a stage 

 when gastrulation was from one-third to one-half completed. The remainder 

 more or less completely closed the blastopore. The anterior portion of 

 embi*3^o is heavy. No eyes and heart were observed. The embryos died 

 three days after closure of the blastopore. 



Gasterosteus bisi/liiosiis, female, 



X 

 Tautoglahrus adsjjersus, male. 

 Seventy-four per cent, in one experiment and practically 100 per cent, 

 in the other were normally impregnated. The embryos developed more suc- 

 cessfvilly than when Tautoga was used as the male. A large per cent, of 

 the eggs attempted to close the blastopore. The anterior end of embryo was 

 large, eyes and heart were develoi)ed but not normally. The embryos lived 

 for five days in this condition. 



Menidia iiotuta, female, 



X 

 Tautoga onitis, male. 

 Eighty per cent, of all the eggs were normally fertilized. The embryos 



