332 SCIENCE FROM AN EASY CHAIR 



changes. The second generation of moths so produced 

 are male and female, but the females, being kept apart 

 again, produce a parthenogenetic brood, and the process 

 has been repeated to a third generation. These instances 

 are very rare. The remarkable thing about them is that, 

 apparently, the parthenogenesis is only due to the experi- 

 mental interference of an entomologist, and that unless 

 some such accident had befallen the moths, the eggs 

 would have been fertilised in the usual way, since there 

 was no deficiency of male moths. These facts have led 

 to many interesting speculations, and are particularly 

 curious in regard to the inquiry as to what determines 

 the sex of offspring, about which sensational announce- 

 ments are sometimes made in the foreign correspondence 

 columns of our newspapers. Here we find the partheno- 

 genetic eggs of the moths producing both males and 

 females, those of the aphides and the pond-shrimp pro- 

 ducing predominantly females, and those of the queen bee 

 producing exclusively males (drones). Biologists have not 

 yet arrived at a solution of the problem raised by these 

 divergent results. 



It is necessary, in regard to this subject, to remember 

 that many lower animals and plants can reproduce or 

 propagate by separating " buds," or large bits of thei 

 bodies, built up of thousands of cells, and, therefore, not 

 to be confused with the single egg-cell. The egg-cell is 

 a cell specially prepared for fusion with a sperm -cell, 

 necessitating except in very rare instances the union 

 in the new individual or young of living material from 

 two separate parental organisms, and, therefore, in many 

 cases, from two widely separate lines of ancestry. A 

 snippet, or bit cut from a begonia leaf, will produce a 

 new individual plant ; a bit cut or torn from a polyp will 

 similarly give rise to a new individual : but the partheno- 

 genetic egg is not to be confused with these masses of 



