914 MB. H. H. BEINDLET ON THE EEGENERATIOX [NoV. 30, 



undoubtedly newly hatched individuals. Between 500 and 600 

 egg-capsules were collected from bakehouses and kitchens in 

 Cambridge, yery mauy of tbera immediately after deposition by 

 the females. 



At first they were placed in an incubator in the Zoological 

 Laboratory in a constant temperature of 38° C, but so little 

 success attended this method that the capsules obtained later 

 were left undisturbed, as nearly as possible in the exact spots 

 where they had been deposited. But from the whole number of 

 capsules observed, only 20 hatchings were obtained, the total 

 number of young thus raised being 210, an average of 10-5 young 

 from each capsule, which in this species normally contains 

 16 embryos. 



If this observation may be regarded as resting on a fairly 

 sufficient number of instances, it would seem that a large 

 proportion of the egg-cases deposited do not hatch out, and 

 also that some of the youug in those that do hatch never 

 appear. As all the cases that hatched did so within a few days 

 after deposition, while the others examined long after were 

 invariably found to be quite brittle and dried up inside, it seems 

 unlikely that the non-hatching of the greater number observed 

 was merely a result of allowing insufficient time for hatching to 

 take place. If this view be accepted, it affords a partial explana- 

 tion of the well-known tardiness with which this species spreads. 

 With regard to the time of j^ear when ecdysis occurred, the 

 following observations were made. The mutilated Cockroaches 

 commenced living in captivity during the first three months of 

 the year. The dates of 235 observed ecdyses were distributed 

 thus : — 



March 4 ecdyses. 



April 12 



May 18 



June 92 



July 72 



August 33 



September .... 4 



That the number of ecdyses during the maximum period 

 increased rather more rapidly than it declined, is apparent from 

 the following : — 



May, 3rd week 4 ecdyses. 



1, 4th „ 8 „ 



12 

 42 



21 „ 



17 „ 



— " 5i 



10 „ 



17 „ 



