296 



pair could equally be experimented on, and afforded some 

 record of the condition of the appendage in the pupa. 



I began by chloroforming my larvae, before injuring them, 

 but found that the chloroform inconvenienced them vastly 

 more than the operation, so that such an efíort to make the 

 operation painless was worse than useless. I believe the larvae 

 experience no pain as we regard it, but I found that anaesthesia 

 was an advantage in handling the larvae, and that this could 

 be secured, without damage or serious inconvenience to the 

 larvae, by drowning. If only reduced to complete anaesthesia, 

 they very rapidly recovered without any apparent ill effect. 



As regards pain, the response to outside agencies is developed 

 as pain in the higher vertebrates to guard the animal against 

 local injury, but in these larvae (and in most insects) local injury 

 is of little comparative moment, and seems hardly to be felt, 

 whereas capture, with a view to being devoured, is a very common 

 accident, and so any interference, suggesting or amounting 

 to capture, produces very grave discomfort and corresponding 

 efforts to escape ; and so in handling my larvae without anaes- 

 thetics, the struggling was great, and the muscular efforts 

 caused the wounds made to bleed, though the actual operation 

 performed produced little reaction. 



The anœsthesia of partial drowning overcame both these 

 difficulties. That of chloroform was generally accompanied 

 by profuse eructations of fluid, and the recovery was usually 

 slow, with debility, due to the vomiting, much in excess of any- 

 thing caused by the operation. 



The photographs (by Mr. F. N. Clark) show the imaginai 

 legs, usually of both sides for comparison, and the larval legs 

 of each moult, from the instar in which the injury occurred 

 onwards, and in some cases the pupal coverings. These are 

 all magnified 7I times, except where a x is placed against the 

 photograph — these are magnified 15 times, twice the amplitude 

 of the others. A few have other magnifications, generally x 20 : 

 these are recorded on the photograph.^ 



In comparing the specimens, this difference must be remem- 



^ The plates are fractionally reduced from the photographs ; exception- 

 ally Plates XVIII and XXIII are reduced nearly as 4 to 3. The relative 

 dimensions of the items in the plates are of course unaffected by this. 



