158 READINGS IN BIOLOGICAL SCIENCE 



counted for the development of sexual differences. The latter also thought 

 that these differences in sex play an important part in bringing about vari- 

 ation. The offspring inherits some characteristics from its father, others 

 from its mother, and hence embodies a new combination of characters. 

 Others have given such obvious explanations of all the facts connected 

 with sexual life that there seems to be nothing which is beyond the com- 

 prehension of these scientists! Do we ask what is the basis of sex-love.' 

 Jaeger puts forward the hypothesis that it consists in a similarity between 

 the exhalations of the male and the female, and in a chemical attraction 

 set up by these exhalations. Pfeffer has actually succeeded in obtaining a 

 proof of this hypothesis in the case of certain plants. Alantegazza also 

 gave a very similar explanation. Others, like Nageli, have considered that 

 the attraction is electrical in nature. 



But why do two cells strive to unite? why the electricity and the chem- 

 ical attraction? The reason is not a very abstruse one! According to some 

 scientists cell conjugation developed from a kind of cannibalism. One 

 cell devoured its neighbour, became strong, passed on the capacity for 

 devouring its neighbour to its successors, and so conjugation began. 

 Jacques Loeb suggests (1906) that fertilization has the following signifi- 

 cance: the spermatozoon brings into the ovum certain chemical sub- 

 stances which hasten segmentation; this can, however, be brought about 

 without the help of the spermatozoon, merely by the influence of cer- 

 tain chemicals. A little potassium chloride or cooking salt is a substitute 

 for the male element, as has been shown at any rate in Echinidae worms, 

 starfish, and other animals. A mechanical stimulus (as has been demon- 

 strated on the frog) may act in the same way. 



Boveri (1902), on his side, compared the egg to a watch which has not 

 been wound up; fertilization simply winds the spring, and this makes seg- 

 mentation possible. According to him the essential factor is the centro- 

 some, which enters the ovum with the spermatozoon. For Herbert Spencer 

 also the object of fertilization was no mystery; life is like a constantly 

 moving wave; the beginning of life resembles the heaving surface of the 

 water; it becomes calmer and calmer as development proceeds; in the 

 ovum such a peace prevails that a new impulse must come to it from out- 

 side; the fertilizing spermatozoon is like a stone thrown into a pond; life 

 is set in motion again, and the power for a new period of development is 

 given.^ 



When we contemplate the activities and struggles of the Universe, it 

 would seem as if the antithesis between male and female plays the most 

 important part in the whole drama. The most beautiful and the most vile 

 in practical life, in philosophy, and in literature, is developed under the 



1 A systematic account of the problems of sex is given by P. Geddes and J. Thomp- 

 son in The Evolution of Sex, 1899; L. Dante, La Sexualite, 1899. H. His gives the his- 

 tory of the subject in "Die Theorien der geschlechtlichen Zeugung," Arcbiv. fiir An- 

 thropologie, iv, 1870 and 1872 (incomplete). 



