400 On Parthenogenesis. 



is now understood that the so-called alternation of generation is 

 nothing more than the successive states exemplified in plants, of* 

 the embryo, incipient leaf bud, opened leaf bud, flower bud and 

 flower, all of which are often widely diverse in forms. 



It was in view of such facts as these that Dr. Burnett under- 

 took to determine the nature of the process of continued non- 

 sexual propagation in the Aphides; and his conclusion was, that 

 the egg-like bodies, developed in clusters within the producing 

 Aphis, were of the nature of buds, and not true ova, agreeing in 

 this with Dr. Carpenter; and that the whole was analogous to 

 the budding process. "The germs/' he says, *' have none of the 

 structural characteristics of eggs, such as a vitellus, a germina- 

 tive vesicle and dot; on the other hand, they are at first, simple 

 collections, in oval masses, of nucleated cells." He also refers 

 to the same kind of origin, the so-called hibernating eggs of 

 Daphnia among Crustacea, Lacinularia among the Rotatoria, and 

 Hydatina and Notommala among the Infusoria, in which, he ob- 

 serves, no germiiiative vesicle or dot has been seen, and no con- 

 nection with the ovary discovered. 



Parthenogenesis in the Aphides, according to this view, is re- 

 production by buds or gemmiparous reproduction, as distinct from 

 sexual reproduction. It is like leaf-budding, the flower-budding 

 (or sexual developments) taking place at longer intervals. 



The later investigations of some zoologists have been tending 

 to the conclusion that even true eggs, or bodies having the struc- 

 ture of eggs in every essential point, may be produced in some 

 cases by females, and develop into perfect individuals without 

 the intervention of the male, and without any proper hermaph- 

 roditism in the parent. The most important work that has 

 appeared on this subject is one on "Parthenogenesis in Moths 

 and Bees," by C. T. E. von Siebold of Munich, which has been 

 translated in England by W. S. Dallas. The author describes 

 the raising of brood after t)rood of young from some moths, with- 

 out the recurrence of a single male; and in a Psyche^ the pupa- 

 case is filled with eggs before it is left ; and in a Selonohia^ the 

 animal immediately after leaving the case, stuffs it full of eggs. 

 The main point in his work, and one of more questionable char- 

 acter, relates to bees. He adopts the theory of a Silesian cler^- 

 man named Dzierzon, and after farther elaborating it, sustains the 

 mow that " the queen-bee, which like all other female insect^ 

 receives the seminal fluid of the male in a peculiar receptacle, 

 ;there to be retained until it comes in contact with the egg during 

 its passage through the oviduct, possesses the power of per- 

 mitting or preventing this contact, so that the eggs may be de- 

 posited in the cells, either fecundated or unfecundated, at tbe 

 p]easure of the mother; and farther, that from the fecundatea 

 *^ggs, female larves are produced which become developed either 



^K 



