Pomona ("m.i.KciK Joirnai. ok E.SToMoiiOov Hfi.'j 



HKITRAGK Zl H KKNNTNIS DKS GENKRAHOrsWKCKSKLS HKI 

 KINKiKN AIMDID.K 



I. KI.<H>N1TSKI 



Zool. .lahrh. Md. XXXIII. U.-ft. 5. 1!)12. 



Tilt' s[)efit'.s considcrt'd in particiilHr an- Siphoiiopiira rosar, Aphix hi'iltrar, 

 A. saleccti, Chai tophariis tixtuilhialiis and ('. arfris. ThtTc an* nunicrouK 

 diagrams and tal)K's. The pcnoral n-sults an- as follows: 



Elvery one of the investigated aphid races pos.sess<>s a single partieular 

 (•yele whieh consists of parthenogenetie and sexual generations. The oocur- 

 renee of the sexual animals and also the other eliaraeters of the cycle, (occur- 

 rence of the winged forms, rest periods of eggs, etc.), are depen<lent upon 

 inner causes. The outer factoi-s i-an only lead to somatic changes, also to such 

 whieh consist of the cheek of development and various different ipiantitativc 

 modifications. I)ut they can call forth no generative changes, which modify 

 the method of propagation in (|ualitative regard. 



There are two particular types of cycles. In one group of individuals 

 with one year there is a complete and close<l cycle. I'ndcr this come the sexual 

 animals for the most part, after a certain nuud)er of the parthcnogcnctic gen- 

 eration. The second grou[) has an incomplete cycle whose geneological stems 

 can propagate themselves unbroken through a very long time by partheno- 

 genesis. Fnnn these stems the branches separate gradually, which en<l with 

 sexual animals. 



