Heredity in Fundulus Hybrids 



147 



account of a fourth and considerably more searching method of 

 comparison, which was used in the last two experiments, precedes 

 Experiment 6. 



The three methods of comparison just described were used in 

 the first four experiments and were in each case mutually con- 

 firmatory. For the sake of brevity and uniformity they will, in 

 each experiment, be designated as follows: 



Method I. Comparison of average number of blastomeres. 



Method II. Comparison of all 4's and all 2's. 



Method III. Comparison of strict 4's, strict 2's and interme- 

 diates. 



EXPERIMENTAL DATA 



Experiment I 



Eggs of several females and milt of two males of each species 

 used. Killed three hours and fortv-five minutes after fertilization. 



TABLE I 



PURE-BRED 



No. of Eggs 



No. of 

 Blastomeres 



No. of Eggs 



No. of 

 Blastomeres 



4-cell 4 



4-minus- ; 3^ 



3-celI ' 3 



2-plus 2i 



2-cell , .' 2 



74 

 62 



33 

 ^6 



296 



217 



99 

 140 



202 



167 



^3 

 28 

 64 



668 



227^ 

 69 

 70 



There were 235 uncleaved eggs in the pure-bred lot and 218 in 

 the hybrid. 



Method I. Comparison of average number of blastomeres. The 

 average in the pure-bred lot is 2.91 +; that in the hybrid lot 



Method II. Comparison of all 4's and all 2's. In the pure-bred 

 lot there are 41.33 + per cent of 4's and 48.63 + per cent of 2's; 

 in the hybrid lot 65.72 + per cent of 4's and 27.76 + per cent of 2's. 



