32 



LECTURE II. 

 ON PARTHENOGENESIS (continued). 



IN the former part of this Introductory Discourse I ad- 

 duced some of the instances in the animal kingdom in 

 which a species is propagated in different ways, and is re- 

 presented by procreative individuals of different forms ; the 

 group of such individuals representing nevertheless one 

 and the same species, and returning into itself. I cited 

 the hypotheses which naturalists and physiologists of de- 

 servedly high repute had propounded for one of the earlier 

 known instances of this cyclical generation, and showed 

 how they failed in their end ; and I proceed now to con- 

 sider the explanations that have been offered by those who 

 have recognized and pondered over a wider range of these 

 phaenomena, and have endeavoured to generalize them. 



With a view to illustrate one of these generalizations, 

 permit me to revert to some of the more simple manifesta- 

 tions of the phaenomena which we were last considering. 



Suppose the Monad to be developed from a germ-cell, 

 and to propagate by spontaneous fission, each individual 

 so formed developing and liberating germ-cells, and these 

 again producing fissiparous individuals*; just as the Hy- 



* On the authority of Ehrenberg. No one however has yet wit- 

 nessed the development of the germ- cell into the Polygastrian ; but this 

 negative fact seems to me to have undue weight given to it when it is 

 made to preponderate against the analogies which have led the masterly 

 Micrographer to his conclusions. The germ -cells, which in well-fed 

 Polygastria occupy the interspaces of the digestive sacs, the rythmical 

 pulsatile sacs and the nucleus, are too regular in their cell -form, and for 

 the most part too much alike, to allow of our dismissing them as of no 

 functional significance under the name of ' sarcode.' M. Dujardin 

 would seem also not to have comprehended the essentials of an ovum 

 and of development from such, in the lowest forms of animals, when 

 he objects to Ehrenberg's interpretation of the cells in question, " pour 

 etre fixe definitivement sur leur nature il faudrait avoir vu au moins des 

 coques vides apres 1'eclosion." (Annales des Sciences Naturelles, t. x. 



