i5« 



THE E VOL UTION OF SEX. 



CHAPTER XIII. 

 DEGENERATE SEXUAL REPRODUCTION OR PARTHENOGENESIS. 



I. History of Discovery. — From very early times there 

 appears to have been an impression, that in exceptional circumstances 

 reproduction might occur without fertilization. Even Aristotle gave 

 reasons for believing that, without sexual union, the unfertilized eggs 

 of the honey-bee might give rise to perfect adults. We now know 

 that he was right, in his conclusion at least, so far as the develop- 

 ment of drones is concerned. In the early belief in Lucina sine 

 coyicubitu, much that was erroneous was intermixed with a prevision 

 of the truth; nor could we expect at an early date that asexual 

 multiplication (that is, apart from ova altogether) would be kept 

 distinct from what we now mean by parthenogenesis, or the develop- 

 ment of ova without union with sperms. In 1701, Albrecht observed 

 that a female silkmoth, which had been isolated in a glass case, laid 

 fertile eggs; and though this was for long discredited, the occasional 

 parthenogenesis of this insect has been repeatedly confirmed by 

 competent observers. 



In 1745 the ingenious Bonnet drew attention to what is now a 

 verv familiar fact — the successive generations of virgin plant-lice or 

 aphides. Throughout the summer, he observed the production of 

 numerous generations of these little insects, all females, necessarily 

 therefore all virgins, and yet fertile. So strange did the fact appear, 

 that it was for long utterly discredited. Reaumur eluded the diffi- 

 culty, by affirming that the aphides were hermaphrodite; but Dufour 

 soon proved that this was erroneous, though he could only confess 

 his ignorance in referring the phenomena to " spontaneous or equi- 

 vocal generation," in which "the act of impregnation was in no 

 degree concerned." The facts, however, were repeatedly re-observed. 

 Kirby and Spence admitted them as incontestable, but could regard 

 them only as "one of the mysteries of the Creator, that human 

 intellect can not fully penetrate." 



Meanwhile Sch'affer had observed the occurrence of partheno- 

 genesis in minute aquatic crustaceans, the study of which has since 

 shed some vivid light on the whole subject. Pastor Dzierzon had 

 also clipped the wings of the queen-bees, and in thus preventing their 

 nuptial flight and impregnation, observed that the eggs they laid 

 developed only into drones. The facts soon began to be recognized, 



