20 SEX 



here we are at the foundation of the differences 

 between the two sexes. But so far as we 

 know there is no " sex- behaviour " in these 

 two kinds of colonies. The minute sperma- 

 tozoa, restless and anarchic from first to last, 

 are set free into the water, and some of them 

 coming into the vicinity of ripe female colonies 

 are attracted to the ova attracted from a 

 slight distance by that more or less mysterious 

 attraction, of which our first germ of know- 

 ledge is expressed in the technical word 

 " chemotaxis." 



SIGNIFICANCE OF CONJUGATION IN PRO- 

 TOZOA. In his fundamental investigations 

 on the conjugation of Infusorians, Maupas 

 inquired into the significance of the process. 

 He asked, for instance, whether the conjuga- 

 tion accelerated subsequent division the 

 ordinary process of asexual multiplication 

 which these Infusorians exhibit. His answer 

 was a decided negative. While a pair of 

 Infusorians (Onychodromus grandis) were 

 engaged in conjugation, a single individual 

 had, by ordinary division, become the ancestor 

 of from forty thousand to fifty thousand 

 individuals. He showed, moreover, that the 

 intricate internal changes associated with 

 conjugation and the subsequent reconstruc- 

 tion, involved a prolonged inertness during 

 which the organisms were exposed to great 

 risks from their enemies. 



Puzzled by this result, Maupas made a 

 more extended series of observations. In 

 November 1885 he isolated an Infusorian 

 (Stylonichia pustulata) and observed its gener- 

 ations till March 1886. By that time there 



