1890.] lUJ [Kyder. 



The Origin of Sex through Cumulative Integration, and the Relation of 

 Sexuality to the Genesis of Species. 



By John A. Ryder. 



(Read before the American Philosophical Society, May 16, 1S90.) 



General Considerations. 



A careful survey of the living world leads to the conclusion that sexual- 

 ity has been, in all probability, one of the many results of the operation of 

 the forces of evolution. A further examination of the evidence discloses 

 the fact that sexuality has arisen very gradually and only through an 

 extensive series of very gentle progressive and successive steps. These 

 steps seem to have had a definite sequence and to have been accompanied 

 by such a gradual complication of means, that it seems highly probable, 

 indeed certain, that in many instances, a given higher grade of sexuality 

 has grown out of the preceding one. This serial superimposition of 

 means to serve apparently more advantageous ends proceeds according 

 to fixed rules or laws, apparently determined by the already attained 

 structural complication and physiological activities of organisms, and in 

 conformity with the controlling conditions offered by their surroundings. 



A still further examination of the data of sexuality leads to the conclu- 

 sion that the methods of it which may be observed in the vegetable 

 and animal worlds have proceeded along two parallel but distinct lines 

 of progress. Both have ended in the achievement of the same re- 

 sult, namely, viviparity or the production of offspring in an advanced 

 state of development, before the latter is set free from the parent to begin 

 an independent existence for itself. An acorn is as truly a product of 

 viviparous development as an infant human being. The elaborate process 

 of organic evolution through which it has been possible to develop the 

 one, is just as wonderful as in the case of the other. 



The end-result of the achievement of viviparity has been to enable 

 forms so produced to survive with far more certainty, and to begin their 

 struggle for existence with a greater chance of success than if the complex 

 series of processes of germ-development, in these cases, had to proceed 

 to the same stage without the elaborate means of protection afforded by 

 the parent. This is so obvious that it seems hardly necessary to call 

 attention to the significance of the gradual complication of sexual pro- 

 cesses. Yet, as one finds the subject usually dealt with, sexuality seems 

 to be regarded, by the majority of writers, as an ultimate fact, and as 

 such, incapable of interpretation in more general terms. 



That sexuality has an important bearing upon some of the most im- 

 portant questions in evolution, no thoughtful biologist would probably 

 doubt. Notwithstanding this, there have been few serious attempts made 

 to grapple with the problem of "sex." Many of the attempts which have 



