112 



THE EVOLUTION OF SEX. 



special reservoirs or spermathecse. So it is with many animals. 

 The spermatozoa received by the queen bee during her single 

 impregnation, are for a considerable period — even for three 

 years — used in fertilising successive sets of worker and queen 

 ova. Quite unique, however, is the case of one of Sir John 

 Lubbock's queen ants, which laid fertile eggs thirteen years after 

 the last se.^ual union with a male. The spermatozoa had ap- 

 parently persisted all that time. Hensen cites the facts, that a 

 hen will lay fertilised eggs eighteen days after the removal of 

 the cock; and that in bats, spermatozoa may remain alive a 

 whole winter in the uterus of the female, {c) Remarkable too, 

 and again like monads, is the power the sperms have of suc- 

 cessfully resisting great deviations from the normal temperature. 

 The presence of acids has usually a paralysing influence, but 

 alkaline solutions have, on the whole, the opposite result. 



Diagram of the Development of Spermatozoa (upper line), of the Maturation and 

 F^ertilisation of the Ovum (lower line). 



a, an amoehoid sex-cell ; A, ovum, with germinal vesicle, n ; B, ovum extruding first 

 polar body, /' and leaving nucleus reduced by half; C, extrusion of second 

 polar body, /'^, nucleus «-, now reduced to one-fourth of original, i, a mother 

 sperm-cell, dividing (2, 3) into immature and mature spermatozoa {x/>.). 



D, the entrance of a spermatozoon ; E, the male and female nuclei s/>. n and n" 

 approach one another. 



§5. Origin of the Sperffis. — 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 spe'rms. 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 



