365 



Ftindtilus JieterocUtiis, female, 



X 

 Gasterosteus bisi)inosus, male. 



The percentage of eggs impregnated maj' be nearly normal, thus : 



Experiment 26cl 86 per cent. 



105d 18 " " 



A very few of the eggs may be polyspermic. The details of the de- 

 velopment of the hybrid and the normals occur in the table following. It 

 will be noticed that the developmental processes keep apace until the close 

 of cleavage. During the formation of the embryo the hybrids fall percep- 

 tibly behind. Most of the eggs go to the closure of the blastopore, although 

 this is accomplished in many eggs only imperfectly. The embryos are 

 largely shorter than the normals, The details of development are item- 

 ized in Table 5. 



Table 5. 



Time. 



FXJNDULUS X FUNDULUS. 



FuNDULUs X Gasterosteus. 



2.40 p. M. 



June 30. 



Fertilization. 



5.00 V. M. 



June 30. 



Well along in 2 cells. 



5.12 p. M. 



June 30. 



Begin. 4 cells. 



5.57 p. M. 



June 30. 



Still in 4 cells. 



6.03 p. M. 



June 30. 



Just begin. 8 cells. 



6.05 p. M. 



June 30. 



Mostly well along in 8 cells. 



11.00 a.m. 



July 1. 



Toward close of segmentation. 



12.30 P. M. 



July 1., 



Late segmentation. 



1.30 p. M. 



, July 1. 



Begin, gastnilation. 



9.00 p. M. 



. July 1. 



i over yolk. 



11.00 A. M. 



, July 2. 



f -\- over yolk. 



12.00 M. 



. July 4. 



Embryos formed, brain vesicles, 

 etc. 



12.00 M. 



, July 7. 



Eyes formed; tall. 



Fertilization. 

 Well along in 2 cells. 

 Begin. 4 cells. 

 Begin. 8 cells. 



Mostly well along in 8 cells. 

 Well along in 8 cells. 

 Toward close of segmentation. 

 I^ate segmentation. 

 Begin, gastrulation. 

 i over yolk. 

 Mostly J + over yolk. 

 Embryos formed but no indica- 

 tion of brain vesicles, etc. 

 About same as in previous stage. 



Ga.'^frrosteufi hifipinofnift, female, 



X 

 FundiiJiifi Jicfcrorlitii.^, male. 

 This cross was made three times, and in one case all the eggs were 

 impregnated. There is the same high mortality usual during gastrulation 

 in these hybrids. Those eggs that laid down the embryo showed the latter 

 very much shortened and the head end very much thickened, many of the 

 embrj^os appearing to be only head. Rudimentary eyes may form. Details 



