DEGENERATE SEXUAL REPRODUCTION. 1 79 



becomes superfluous to the species. (2.) He also allows that it 

 does degenerate in the summer aphides, where the periodic 

 disappearance of males is well known. (3.) In spite of the 

 absence or else futility of impregnation in rotifers, we find the 

 males obviously in process of degeneration. 



In conclusion, we believe with Weismann and others, that 

 the absence of fertilisation is a minus in evolution, but see no 

 warrant for supposing that it absolutely precludes either pro- 

 gress or the reverse. The power of parthenogenetic birth has 

 two different results. (i.) The female cell has a certain 

 maleness about it ; it retains the stimulus which the male ele- 

 ment usually affords ; the species will therefore be frequently 

 of active male -like habit, e.g., rotifers and water-fleas. (2.) On 

 the other hand, the long continued production of females 

 means an anabolic preponderance, 'a weighting of the species ; 

 and this is seen in the sluggish plant-lice, coccus insects, and 

 the like. 



§ 7. Pecidia7'ity of the Parthenogenetic Ova. — Before a theory 

 of parthenogenesis is sought, the natural question arises. Are 

 these eggs that develop of themselves in any way peculiar? 

 {a) For a while it was supposed {e.g., by Balfour) that 

 parthenogenetic ova did not form polar globules, and the 

 theory based upon that regarded the retention of these bodies 

 as taking the place of fertilisation. The demonstrated occur- 

 rence of one polar globule in several parthenogenetic eggs 

 partially demolished this theory, and it is only within the last 

 two or three years that it has been restated in accurate form. 

 ip) Simon shrewdly points out, that in some of the most 

 marked cases of parthenogenesis the sex-cells are insulated 

 from the body at a very early stage. This is notably so in 

 those midges which reproduce parthenogenetically even before 

 maturity. It is certainly striking that these forms should 

 unite an extreme earliness in the embryonic separation of 

 the germ-cells with a most precocious reproduction. These 

 germ-cells are ova which have a much less circuitous history 

 than in most cases ; they have far fewer cell-divisions behind 

 them, they have thus a reserve power of division which other 

 ova have not ; they are able, in fact, to develop of themselves. 

 This, unfortunately, is not known to be true of some of the most 

 signal cases of parthenogenesis {e.g., rotifers) ; but it is true of 

 some, and that to a greater extent than was know^n when Simon 

 wrote. On the other hand, some forms where parthenogenesis 



