VII PARTHENOGENESIS 259 



male sperm elements, and proceed to develop as female 

 individuals. 



The second chapter, very short, is on Partheno- 

 genesis in Vespa Jiolsatica, which was inferred to 

 occur from the observation of a naturally -produced 

 queenless colony, the larvce in the cells of which were 

 all male. 



The third chapter is on Parthenogenesis in Nematus 

 ventricosus, the larva of which is known as the Goose- 

 berry-caterpillar. Since three or more generations of 

 these leaf-wasps occur in the season, they furnished 

 abundant material, and the old supposition of partheno- 

 genesis first put out as regards them by Robert Thorn, 

 in the Gardeners Magazine, 1820, is shown by 

 Siebold to be justified by carefully conditioned experi- 

 ment. Some valuable observations on the anatomy 

 of the generative organs, and on the curious increase 

 in the size of the egg after it is laid, are given. The 

 parthenogenetically produced progeny are in this case 

 also male. The results of the Nematus experiments 

 were not ready for publication until after the issue of 

 the present work, and we have received, through the 

 kindness of Dr. Dohrn, a copy of the Sitzungsberichte 

 of the Munich Academy of 4th November 1871, in 

 which they are fully given. It appears that though 

 an occasional female appeared among the male broods 

 produced by unfertilised females, this was, in every 

 case where it happened, fully accounted for by the 

 accidental access of a fertilised female, or some such 

 misadventure, duly noted in the records kept of the 

 observations. 



