( vii ) 



and a series of M. neitstria iov comparison with a hybrid 

 brood, resulting from a pairing between a male neustria and 

 a female castrensis. Only a portion of the batch of from 200 

 to 300 ova that the female laid hatched. Of the ova that did 

 not hatch, some wei'e found to contain fully-developed, but 

 dead larva, while in other instances the eggs were qviite empty. 

 Continuing, Mr. Bacot said : — " The young larvje were healthy 

 and did not differ perceptibly from a brood of young castrensis, 

 except in regard to their rapidity of growth. Either just 

 before or just after their second moult the brood divided into 

 two portions ; one of which grew rapidly and the other very 

 slowly, so that it became necessary to separate them for con- 

 venience of feeding. The ' forwards ' were very healthy — I 

 do not remember a single death — and they fed up at an unpre- 

 cedented rate, producing the female specimens exhibited. 

 The * laggat-ds ' fed slowly, were unhealthy, and weakly, the 

 total number of emergencies being seven out of some thirty 

 that spun up ; these were all males, and, judging by the size of 

 the larvse, the remainder of the ' laggards ' that did not 

 emerge were of this sex. The last of the females that 

 emerged was three weeks ahead of the first male, and most 

 unfortunately before any males of either of the parent species, 

 so that the fertility of the hybrid females could not be tested. 

 Their bodies apparently contain few, if any, ova. I have every 

 reason to believe, however, that I obtained pairings between 

 the hybrid males and females of castrensis, in addition to 

 fresh pairings between males of neustria and females of 

 castrensis, and therefore have hopes of continuing the experi- 

 ment next summer." 



Mr. J. W. TuTT said this was the first time any exhibition 

 of experiments of the kind had been made before the Society 

 by British investigators, though Mr. Merrifield had shown a 

 number of crosses bred by Herr Standfuss. Tn this case the 

 colouring of the $ hybrids, departing from the usual colour 

 of the 5 s of the parent species, appeared to approach more 

 nearly in tint to the 9 s of the closely-allied Alpine species 

 Malacosoma al/ncola, and it would be interesting to discover 

 whether this peculiarity of colour in the hybrid ? s really 

 marked a tendency to revert to a more primitive $ type of 



