REPRODUCTION OF APHIDES. 685 



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 Viviparous 

 hrood that repeat the curious life-history of their predecessors. It 

 appears from the observations of Prof. Huxley,* that the broods of 

 Viviparous Aphides originate in ova which are not to be distin- 

 guished 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 ' Generation ;' for it is favoured, 

 like the gemmation of Hydra (§ 411), by warmth and copious 

 sustenance, so that by appropriate treatment the Viviparous repro- 

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

 without any recurrence to the Sexual process. Recent observa- 

 tions render it probable 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 virgin or unimpregnated Queens, 

 occasionally lay eggs, from which eggs none but Drones are ever 

 produced. From careful Microscopic examination of the Drone 

 eggs laid even by impregnated Queens, Siebold draws the conclu- 

 sion that they have not received the fertilizing influence of the 

 Male fluid, which is communicated to the Queen-eggs and Worker 

 eggs alone ; so that the products of Sexual generation ax*e always 

 Females, the Males being developed from these by a process which 

 is essentially one of Gemmation. f 



534. Arachnid a. — The general remarks which have been made 

 in regard to Insects, are equally applicable to this Class ; which 

 includes, along with the Spiders and Scorpions, the tribe of 

 Acarida, which consists of the Miles and Ticks. Many of these 

 are Parasitic, and are popularly associated with the wingless para- 

 sitic Insects, to which they bear a strong general resemblance, 



' 'On the Agamic Reproduction and Morphology of Aphis,' in 

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



t See Prof. Siebold's Memoir " On time Parthenogenesis in Moths and 

 Bees," translated by W. S. Dallas ; London, 1857. 



