COCKROACHES, ETC. 155 



ultimate fate I hope to be able to witness uninter- 

 ruptedly. 1 



1 Mr. Shelford exhibited, in 1908, a specimen of this stock bred by 

 Mr. H. Main(Proc. Ent. Soc., 1908, p. Ixxvi). Mr. Shelford's breeding 

 experiment is still (1916) being continued in Oxford by Mr. J. B. 

 Baker, M.A. The insects thrive upon privet. As yet no male 

 has been observed in Oxford, but a single one was bred by Mr. 

 K. G. Blair in London from the same stock (Proc. Ent. Soc., 1911, 

 p. Ixi). The parent is believed to have come originally from India, 

 but the species has not been made out with certainty. The in- 

 sects are generally referred to the Indian species Dixippus or Carau- 

 sius morosus, although others have considered that they are an 

 undescribed species of Menexenus, or of Lonchodes. Mr. H. Ling 

 Roth has in recent years reared to maturity about 1,200 individuals 

 in four generations, at Halifax, Yorkshire. Among these one single 

 male appeared in the third generation. Mr. Ling Roth has made 

 careful measurements of the size of various parts, the length of 

 stages, etc., proving that variation is strongly marked in these 

 parthenogenetically bred individuals a conclusion of great im- 

 portance in relation to Weismann's well-known theory of the role 

 of sexual reproduction in causing variation. E. B. P. 



