ON THE NUMBER OF POLAR BODIES AND 

 THEIR SIGNIFICANCE IN HEREDITY. 



PREFACE. 



THE following- paper stands in close relation to a series of short 

 essays which I have published from time to time since the year 

 1 88 1. The first of these treated of ' The Duration of Life,' and the 

 last of ' The Significance of Sexual Reproduction.' The present 

 essay is most intimately connected with that upon ' The Continuity 

 of the Germ-plasm/ and has, in fact, grown out of the explanation 

 of the meaning- of polar bodies in the animal egg, brought forward 

 in that essay. The explanation rested upon a trustworthy and solid 

 foundation, as I am now able to maintain with even greater con- 

 fidence than at that time. It rested upon the idea that in the egg-- 

 cell, a cell with a high degree of histological differentiation, two 

 different kinds of nuclear substance exert their influence, one after 

 the other. But continued investigation has shown me that the 

 explanation built upon this idea is only correct in part, and that it 

 does not exhaust the full meaning of the formation of polar bodies. 

 In the present essay I hope to complete the explanation by the 

 addition of essential elements, and I trust that, at the same time, 

 I shall succeed in throwing new light upon the mysterious problems 

 of sexual reproduction and parthenogenesis. 



It is obvious that this essay can only contain an attempt at an 

 explanation, an hypothesis, and not a solution which is above 

 criticism, like the results of mathematical calculation. But no 

 biological theory of the present day can escape a similar fate, for 

 the mathematical key which opens the door leading to the secrets of 

 life has not yet been found, and a considerable period of time must 

 elapse before its discovery. But although I can only offer an hypo- 



