64 TWELFTH REPORT. 



THE ORIGIN OF THE SECOND POLAR BODY. 



CHARLES E. BARR. 



A number of years ago I presented to the Academy a paper showing 

 the origin of sexualify from asexual dimorphism. In this paper I offered 

 a theory of the first pohir body tliat time has served only to confirm. 

 At that time I had not developed a fully satisfactory theory of the 

 second polar body, though the paper indicated the line along which the 

 answer should be sought. 



The problem is by no means a simple one, involving, as it does, a 

 complex interrelation of forces, the principles governing whose action 

 have not yet been fully ascertained. I believe, however, that the time 

 has now come when, through a process of exclusion, a fairly satisfactory 

 conclusion may be reached. 



Fertilization involves two processes, or two steps, of which the second 

 is not necessarily present. These are: the entrance of the sperm into 

 the ovum and the union of the germ nuclei to form a segmentation 

 nucleus. It has been abundantly shown that a spermatozoon, entering 

 an eg^ from which the nucleus has been removed, may yet inaugurate a 

 full development. This obviously is due to the activity of the sj^erm alone, 

 as has been conclusively demonstrated. A spermatozoon, then, under 

 such favorable environmental conditions as thus afforded, can itself 

 develop a new organism. 



As shown in my previous paper, both ovum and sperm must have de- 

 veloped as asexual organisms, each of which, primitively had the capac- 

 ity of independently continuing the race. In the case above cited, it is 

 evident that this capacity has not necessarily been entirely lost in the 

 case of the sperm. Possibly in some of the cases of parthenogenetic 

 development the same may prove true of the ovum. However this may 

 be, the case of Amoeba and other protozoans is sufficient to establish 

 its truth. 



Passing over the causes for the formation of the first polar body, 

 which were adequately treated in my first paper, the crux of the prob- 

 lem, for the second, lies in the reducing division of the chromosomes 

 which occurs preparatory to fertilization. It is evident that this cannot 

 have arisen in '^pi-eparation'' for an event that has not yet entered into 

 the history of the race. Foresight is rare enough in mankind, and in 

 animals it is assuredly a misnomer for hindsight, perpetuated. In 

 seeking for the explanation of the phenomenon, therefore, we must look 

 to the environmental conditions presented to the asexual, dimorphic 

 individuals possessing the full number of chromosomes — and further, 

 we must conceive the reducing division as primitively a result, rather 

 than a preparation for fertilization, which has, in some way, been thrust 

 back in the series of developmental stages, according to the well known 

 principles of tachygenesis. 



The solution of the problem, once these principles are grasped, is so 

 simple that it is astonishing that they have so long escaped the attention 



