VIEGINAL EEPKODUCTION. 197 



one of two generative substances, either the male or the 

 female. The female individuals, both in animals and plants, 

 produce eggs or egg-cells. The eggs of plants in the case 

 of flovrering plants (Phanerogama), are commonly called 

 " embryo sacs " ; in the case of flowerless plants (Crypto- 

 gama), 'fruit spores." In animals, the male individual 

 secretes the fructifying sperm (sperma); in plants, the 

 corpuscles, which correspond to the sperm. In the Phane- 

 rogama, these are the pollen grains, or flower-dust ; in the 

 Cryptogama, a sperm, which, like that of most animals, 

 consists of floating vibratile cells actively moving in a 

 fluid — the zoosperms, spermatozoa, or sperm-cells. 



The so-called virginal reproduction (Parthenogenesis) 

 offers an interesting form of transition from sexual repro- 

 duction to the non-sexual formation of germ-cells (which 

 most resembles it) ; it has been demonstrated to occur in 

 many cases among Insects, especially by Siebold's ex- 

 cellent investigations. In this case germ-cells, which 

 otherwise appear and are formed exactly like egg-cells, 

 become capable of developing themselves into new indi- 

 viduals without requiring the fructifying seed. The most 

 remarkable and most instructive of the different partheno- 

 genetic phenomena are furnished by those cases in which 

 the same germ-cells, according as they are fructified or not, 

 produce different kinds of individuals. Among our common 

 honey bees, a male individual (a drone) arises oufc of the 

 eggs of the queen, if the egg has not been fructified ; a 

 female (a queen, or working bee), if the egg has been fructi- 

 fied. It is evident from this, that in reality there exists 

 no wide chasm between sexual and non-sexual reproduc- 

 tion, but that both modes of reproduction are directly 

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