198 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



statement of Von Siebold, that the hermaphrodite 

 bees, which occasionally occur in great abundance 

 in hives, are due to imperfect fertilisation. 



It is becoming abundantly evident that the phe- 

 nomenon of parthenogenesis in the Insecta is much 

 more complex and extended than was formerly 

 believed. Yon Siebold,* from his observations on 

 Polistes, concluded (1) that the eggs bring with 

 them from the ovary the capacity of differentiating 

 themselves as males ; (2) that they have the power 

 of developing themselves, without male influence, 

 into male individuals ; (3) that the same eggs can 

 be changed in these properties by the influence of 

 the male sperm elements, and proceed to develop 

 into female individuals. 



We now know that the eggs can develop them- 

 selves, without male influence, into female individuals,, 

 even in species which ordinarily produce males and 

 females after fertilisation. Until recently it was 

 believed that there was no material distinction 

 between parthenogenetic and sexual ova ; but the 

 remarkable researches of Weismann have demon- 

 strated the incorrectness of that view. In most 

 eggs there are certain spindle-shaped bodies usually 

 called "polar globules." Before embryonic develop- 

 ment can take place, it is essential that at least one 

 of the polar bodies be thrown out. The first body 

 takes away half of the nuclear substance called by 

 Weismann " ovogenetic plasma," which appears to 

 be detrimental to the development of the egg, for 

 it is thrown out from all eggs. If a second globule 

 be extruded, it takes away one-half of the remaining 

 nuclear substance ; but this latter part is different 

 from that which was removed with the first polar 

 body, being what Weismann calls " germ-plasma " — 

 the germ-plasma being the principal agent in building 

 up the embryo, and the bearer, as it were, of all 

 the properties, physical or otherwise, which distinguish 

 one animal from another. 



*Beitr. zur Parth. der Arthr., p. 101. 



