604 



SCIENCE. 



[N. S. Vol. I. No. 22. 



tive 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 dif- 

 ferences of behavior of the two sorts of sex- 

 cells seem to be correlated with their dif- 

 ferences in size. 



We may contemplate the sex-cells as 

 molecular mechanisms which, in virtue 

 of their mechanical structure, are ren- 

 dered capable of controlling the order 

 and manner of rearrangement of their con- 

 stituent molecules, because of the new suc- 

 cessive attractions and repulsions set free, 

 amongst the latter, immediately upon the 

 completion of conjugation. The new forms 

 of metabolism thus initiated enable us to 

 conceive a mechanical theory of fertiliza- 

 tion. 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 recip- 

 rocally and mechanically 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 oper- 

 ate can actually be to some extent traced, 

 as expressed in the complex movements as- 

 sociated with fertilization, the division of 

 the chromosomes and centrosomes. The ef- 

 fect of conjugation is to afford opportunity 

 also for new and various combinations of 

 molecular mechanisms, though the recipro- 

 cal integration of pairs of cells having a 

 wideljr different parentage. 



The great size of the egg-cell provides an 

 extensive reserve material that enables the 

 embryo thus built up usuallj' to reach a rel- 

 atively great size without entering for a 

 time into competition for food in tlie strug- 

 gle for existence. Sexualitj' 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 -w-ith natural 

 conditions. While it may be assumed that 

 sexuality has arisen, in the main, under 

 conditions determined by natural selection, 

 once sexuality was attained, the added 

 power thus accumulated potentially in large 

 germs of double origin enabled the latter 

 the more easily to overcome untoward 

 natural conditions. N"atural selection thus 

 becomes altruistic or dotational in that it 

 tends through sexualitj' to defeat the deadli- 

 ness of the struggle for existence, just as 

 we may also assert that the theory of super- 

 position to which the mechanical theory of 

 development is committed is also finally 

 altruistic. It may be remarked that the 

 gi-eatest mortality of a species, under the 

 conditions of the struggle for existence, 

 also takes place in the egg and embrj^onic 

 stages, or before organisms can experience 

 acute pain ; so that here again we have a 

 result that must matei'ially ameliorate the 

 pains and penalties of the struggle for 

 life. 



These details are, however, of minor im- 

 port for us just now. The important thing 

 to bear in mind is that all of the forces of 

 development are ultimately metabolic in 

 origin, and that the wonderful order and 

 sequence of events in any given ontogeny 

 arise from the transformation or transposi- 

 tion of the parts of a molecular sj'stem that 

 also thus increases in bulk by the addition 

 of new matter. The steps of this trans- 

 formation are mechanically conditioned by 

 dynamical laws with as much unerring eer- 

 taintj' of sequence as those that control the 

 motions of the heavenly bodies. The con- 

 sequence of such a view is that we can thus 

 free our minds of all traces of belief in a 

 theory of preformation. The embryo is not 

 and cannot be preformed in the germ, as 



