io6 



THE EVOLUTION OF SEX. 



the power the sperms have of successfully resisting great deviations 

 from the normal temperature. The presence of acids has usually a 

 paralyzing influence, but alkaline solutions have, on the whole, the 

 opposite result. 



V. Origin of the Sperms. — A primitive female cell in the ovary 

 grows in bulk and nutriment, and remains intact, but a primitive male 

 cell in the testis undergoes repeated division into secondary cells, 

 which either themselves, or by further division, form the sperms. For 

 the last twenty years the development of spermatozoa has been the 

 subject of almost continuous research and controversy, and the all too- 

 abundant nomenclature affords a suggestive index to the confusion out 



FlG. 29. — Diagram of the Development of Spermatozoa (upper line), of the Maturation and Fertili- 

 zation of the Ovum (lower line). 



a, an amceboid sex-cell ; A, Ovum, with germinal vesicle, «; B, Ovum extruding first polar body, 

 p\ and leaving nucleus reduced by half; C, extrusion of second polar body, p2, nucleus «2, now 

 reduced to one fourth of original. 1, a mother sperm-cell, dividing (2, 3) into immature and 

 mature spermatozoa (sp. ). 



D, the entrance of a Spermatozoan ; E, the male and female nuclei sp. >i and «2 approach one 

 another. 



of which the subject is now emerging. In a general way, the process 

 is simply that of the varied segmentation of a mother-sperm-cell, and 

 the occurrence of a series of preparatory stages before the sperm is 

 finally matured. In detail, however, there are many variations, and 

 these are described in a maze of often tautologous and ambiguous 

 terms, such as spermatogonium, spermatoblast, spermatospore, sperma- 

 togemma, spermatomere, spermosphere, and a dozen more. 



One of the most defensible set of terms is that used by Voigt after Semper, 

 and also by Von la Valette St. George, who has worked persistently at the 

 subject for over twenty years. The sperm or spermatozoan is differentiated 

 from an immature cell or spermatide ; this is modified from or descended from 

 a spermatocyte ; the spermatocytes result from the division of the mother-sperm 

 cell or spermatogonium ; and this finally is a modified form or a descendant of 

 the primitive sex-cell or male ovule. 



