460 Mr Brindley, Regeneration in Samia ailanthus. 



suggested by Newport's result that there is great want of uni- 

 formity in the regeneration of the limb of a pupating insect after 

 a particular injury. Hence it seemed desirable to obtain a number 

 of cases of the results of particular injuries in particular instars, 

 especially as Newport's cases were too few to permit any general 

 conclusion being arrived at. I am indebted to Miss F. Durham for 

 kindly placing at my disposal a large number of caterpillars of 

 Samia ailanthus which were being reared in the Balfour Laboratory, 

 Cambridge, in 1899 and 1900. The results were unfortunately 

 somewhat limited, in consequence of the very large number of 

 failures to emerge from the pupa, an event which had apparently 

 nothing to do with the mutilations inflicted, for, as frequently 

 happens under artificial conditions, the mortality was very high in 

 the pupal state among the whole set of larvae in the laboratory. 

 The experiments made were as follows. 



(.4) Instar of body-length 2*0 to 25 cm. and of pale yellow 

 colour turning to white. This is probably the instar but one 

 before pupation. The injury inflicted was amputation of the third 

 leg in its basal joint by scissors. Unfortunately only four imagos 

 were obtained. The imaginal leg was well developed as regards 

 femur and tibia, but in one case the tarsus was 3-jointed and in 

 the other three 4-jointed, and in only one case (one of the 

 4-jointed tarsi) were the terminal claws well developed. In the 

 other three they were entirely absent, and the tarsal joints were 

 not well formed though their articulations were distinct. In one 

 of those with a 4-jointed tarsus the pupal period was 300 days 

 (August to July) and in the other two 63 days (August to October), 

 while the case with a 3-jointed tarsus was 307 days in pupa. The 

 single case in which the claws were developed was one of the 

 63 days' pupas. Hence, though the number of cases is far too 

 small for certainty, there is a suggestion that the length of time 

 spent in pupa does not affect the degree of regeneration. 



(B) Instar of body-length 3*5 to 4 - cm., and spinning about 

 8 days after mutilation, so that probably the instar was the one 

 which pupates, though I was unable to ascertain this point with 

 certainty. The injury was amputation of the posterior leg in the 

 basal joint. The average number of days spent in pupa was 61. 

 Eleven imagos were obtained, and the leg was regenerated in all, 

 though in a very variable manner. The femur was well developed 

 in about half the cases, and stunted in the others. Tibia and 

 tarsus were sometimes distinguishable, but the tibia and femur, 

 and tibia and tarsus respectively were apparently fused together 

 in certain cases, while the tarsus when recognisable had never 

 more than four joints. In about half the cases the claws were 

 more or less distinctly suggested, as was also a terminal lobe 

 apparently representing the palpal apparatus. 



