A DYNAMICAL HYPOTHESIS OF INHERITANCE. 35 



still in more or less close nutritive relation to the parent; in 

 the egg the " reducing division " or expulsion of polar cells 

 does not occur till the egg is freed, as a rule, from the parent 

 gonad, and generally as a consequence of the stimulating effect 

 of the presence of the male cell. These differences of behav- 

 ior of the two sorts of sex-cells seem to be correlated with 

 their differences in size. 



We may contemplate the sex-cells as molecular mechanisms 

 which, in virtue of their mechanical structure, are rendered 

 capable of controlling the order and manner of rearrangement 

 of their constituent molecules, because of the new successive 

 attractions and repulsions set free, amongst the latter, imme- 

 diately upon the completion of conjugation. The new forms 

 of metabolism thus initiated enable us to conceive a mechani- 

 cal theory of fertilization. At any rate, the two sorts of sex- 

 cells are potentially the reciprocals of each other, and their 

 initial or statical states cannot begin to set free their energy 

 and thus pass into the successive kinetic states of formal 

 change until the two mechanisms are reciprocally and mechan- 

 ically integrated into a single one by means of conjugation. 

 The parts of this new single body now act in unison. Even 

 the manner in which the two conjoined molecular mechanisms 

 operate can actually be to some extent traced, as expressed in 

 the complex movements associated with fertilization, the divi- 

 sion of the chromosomes and centrosomes. The effect of con- 

 jugation is to afford opportunity also for new and various com- 

 binations of molecular mechanisms, through the reciprocal 

 integration of pairs of cells having a widely different parentage. 



The great size of the egg-cell provides an extensive reserve 

 material, that enables the embryo thus built up usually to 

 reach a relatively great size without entering for a time into 

 competition for food in the struggle for existence. Sexuality 

 is therefore altruistic in nature, since it has led in both plants 

 and animals to the evolution of a condition of endowment, or 

 the storage of potential energy in the germ, so that the latter 

 is the better able to cope with natural conditions. While it 

 may be assumed that sexuality has arisen, in the main, under 

 conditions determined by natural selection, once sexuality was 



