352 Mr. H. Ling Roth's observations on 



As regards the quantity of fertile eggs hatched out, the 

 highest percentage was reached from the box, thus : 

 B = 95-1%, M = 92%, and S = 82-8%. 



In this experiment in no case was any nymph found to 

 have succumbed through inability to emerge completely 

 after once breaking through, as happens occasionally to 

 the extent of about five per thousand in the usual 

 incubating-box arrangements. 



The fact that on the mould the incubation proceeded 

 quickest would tend to show that it is the best of the three 

 media, for, in Nature, the quicker this process goes on the 

 less risk to the embryo — the lesser number hatched out 

 being a sacrifice to the safety of the existence of the species. 



Whether the corrosion, if I may so call it, of the eggs from 

 the mould has anything to do with lowering the percentage 

 of hatching out I am unable to say, but it would appear 

 that the natural risks being overcome or reduced to a 

 minimum in the box incubation, that method is the best 

 for laboratory experiment. 



Parthenogenesis. 



These stick insects belong to a Family in which partheno- 

 genesis appears to be the rule, and my experience with 

 them bears out the existence of the general law. The 

 female from which I reared 354 insects up to the egg- 

 bearing stage may or may not have been fertilised by a 

 male. Her offspring were allowed to mix freely with one 

 another until the last ecdysis was reached, when they were 

 successively segregated, and every one of these which 

 reached maturity dropped eggs. The assumption is, that 

 there was consequently no male amongst them. Subse- 

 quently I separated 34 larvae (offshoots of some of the 354) 

 on hatching out, and these with one exception all turned 

 out egg-bearers. The one exception, No. 40, had a mal- 

 formation at the penultimate abdominal segment, and 

 took 170 days to get through the nymph stadia, instead of 

 the average 136 days. It was a poor eater, consuming 

 about one-sixth of the food consumed by the others, and 

 remained thin and lethargic to the end. 



A Male. 



I had one other non-egg-producer, a descendant of one 

 of Dr. Clubb's lot, which turned out to be a male. Dr. 

 Imms dissected it, and found " well-developed reproductive 



