Siebold's Remarks on the Psychidoe. 235 



to attain their development, must previously be fecundated by 

 the semen of the male ; but this phenomenon, observed in Talce- 

 poria, must be added to those widely spread occurrences in the 

 lower orders of animals which we have but recently learnt to es- 

 timate correctly, and now know under the designation of alterna- 

 tion of generation. We should therefore no longer consider the 

 individuals capable of propagation without intercourse with the 

 male, as females endowed with ovaries, but as sexless individuals 

 quite different from females in their organisation. These indivi- 

 duals, sexless, yet capable of propagation, as we have now learned 

 to know them so plentifully among the invertebrata, have been 

 designated Nurses by Steenstrup, who first paid attention to the 

 change of generation. These nurses can propagate by longitu- 

 dinal or transverse section, by external or internal formation of 

 germs, or by a germ-stock. This germ-stock supplies the place 

 of an ovary, and renders the presence and influence of a testicle 

 unnecessary. Such a germ-stock produces in consequence no 

 eggs, but germs (germ-grains or germ-balls). 



According to this physiological law, only recently recognised, 

 the long known wonderful phenomenon among the Aphides is es- 

 timated quite differently from what it has hitherto been. There 

 do not occur in them, in the course of a summer, generations and 

 generations of exclusively female individuals one after another 

 without any traces of male individuals, till at last there appears a 

 brood of male and oviparous female Aphides, which must copulate 

 and be impregnated; but we shall have to consider these vivipa- 

 rous female individuals as sexless nurses provided with germ-stocks. 

 That these Aphis nurses, in reference to their organs of propaga- 

 tion, have a truly different organisation from the oviparous Aphis 

 females, I have already demonstrated in the year 1839 (see 

 "Froriep's Neue Notizen, Band XII. p. 307). The sexless vivi- 

 parous Aphides want not only the receptaculum seminis, which the 

 sexual oviparous Aphides possess, but also the germ-stocks of these 

 Aphis nurses show an entirely different form and structure to the 

 ovaries of the female Aphides. I have already mentioned my 

 suspicion (see my " Lehrbuch der vergleichenden Anatomie der 

 wirbellosen Thiere," p. G34), that the occurrence of sexless nurses 

 among insects was not confined to the single family of the Aphides, 

 and that probably also among the species of Cijnips and Psyche 

 similar nurse formations might occur. In the Psijchidce this is 

 now certainly the case, since the Talceporice are subject to such 

 a change of generation. The account of Lepidopterologists (con- 

 stantly repeated, and from different quarters), that the females 



