378 
SUMMARY OF EXPERIMENTS. 
INTRODUCTORY. . 
In the preceding detailed account of the various crosses effected are 
included combinations between forms of teleosts, ranging from closely re- 
lated species within the same genus to species belonging to widely separated 
orders. ‘Cheir relationships are summarized below, the figures set opposite 
each indicating the number of different combinations made in each group :' 
Between different species of same genus................ 2 
i si genera of same family............... 4 
ts a families of same order...............1 
He ad orders of same class................ 17 
A number of interesting facts appear from the above table and from a 
closer inspection of the more detailed Table 9. In all the crosses attempted 
with the exception of the cross in which Opsanus tau was used as the male. 
impregnation was possible. The sperm of the single Opsanus tau specimen 
used was not ripe in the three combinations attempted, so that it is impossi- 
ble to say whether these crosses are possible. 
CHARACTER OF IMPREGNATION. 
In many of the crosses the impregnation was wholly normal. In some 
there was in addition to the normally impregnated eggs, a varying number 
of dispermic and polyspermic impregnations. Among the abnormally im- 
pregnated eggs the dispermic was very much more common than the poly- 
spermic condition. In the dispermic eggs the protoplasmic disc, as is well 
known, falls at once into four cells. Sections of these conditions show that 
two male pronuclei fuse with the egg pronuclens ; whether additional spermi- 
tozoa enter such eggs, but remain functionless so far as early cleavage is 
concerned, IT am not able to say. In the polyspermic eggs the protoplasm 
falls at once into six or more cells. The cases Coming under my observa- 
tion in which many cells at once appeared, have been rather rare. 
PERCENTAGE OF FERTILIZATION. 
A striking fact is the large percentage of eggs impregnated. In fully 
two-thirds of the crosses this ran above 50 per cent., and in many of the 
cembinations it ran above 75 per cent. A glance at Table 9 will show that 
this is not in any way correlated with the nearness of relationship. 
1 This is represented in more detailed form in Table 9. 
