INSECTS AND ARACHNID A. 247 



the non-sexual reproduction of Entomostraca ( 609) and Rotifera ( 451) 

 as also of Hydra ( 515) and Zoophytes generally; all of which fail spe- 

 cially, most of them exclusively, under the observation of the Microscopist. 

 The Aphides which may be seen in the spring and early summer, and 

 which are commonly but not always wingless, are all of one sex, and 

 give birth to a brood of similar Aphides, which come into the world 

 alive, and before long go through a like process of multiplication. As 

 many as from seven to ten successive broods may thus be produced in the 

 course of a single season; so that from a single Aphis, it has been calcu- 

 lated that no fewer than ten thousand million millions, may be evolved 

 within that period. In the latter part of the year, however, some of these 

 viviparous Aphides attain their full development into males and females; 

 and these perform the true Generative process, whose products are eggs, 

 which, when hatched in the succeeding spring, give origin to a new vivi- 

 parous brood that repeat the curious life-history of their predecessors. 

 It appears from the observations of Prof. Huxley, 1 that the broods of 

 viviparous Aphides originate in ova which are not to be distinguished 

 from those deposited by the perfect winged female. Nevertheless, this 

 non-sexual or agamic reproduction must be considered analogous rather 

 to the < gemmation ' of other Animals and Plants, than to their sexual 



FIG. 437. 



Eggs of Insects, magnified; A, PontianapijB, Vanessa urticce;c, Hipparchiatithous; D Aravn- 

 nis Lathonia. 



( generation;' for it is favored, like the gemmation of Hydra, by warmth 

 and copious sustenance, so that by appropriate treatment the viviparous 

 reproduction may be caused to continue (as it would seem) indefinitely, 

 without any recurrence to the sexual process. Further, ib seems now 

 certain that this mode of reproduction is not at all peculiar to the 

 Aphides, but that many other Insects ordinarily multiply by ( agamic ' 

 propagation, the production of males and the performance of the true 

 generative act being only occasional phenomena; and the researches of 

 Prof. Siebold have led him to conclude that even in the ordinary economy 

 of the Hive-bee the same double mode of reproduction occurs. The 

 queen, who is the only perfect female in the hive, after impregnation by 

 one of the drones (or males), deposits eggs in the ' royal' cells> which are 

 in due time developed into young queens; others in the drone-cells, which 

 become drones; and others in the ordinary cells, which become workers or 

 neuters. It has long been known that these last are really undeveloped 

 females, which, under certain conditions, might become queens; and it 

 has been observed by bee-keepers that worker-bees, in common with 

 . 



1 ' On the Agamic Reproduction and Morphology of Aphis,' in " Transact, of 

 Linn. Soc.," Vol. xxii., p. 193. 



