ON INSECT ANATOMY. 399 



without its general as well as scientific interest. Does the sense 

 of pain or pleasure influence the movements of insects ? Is there 

 any consciousness of sensation or retention of past sensation in 

 the form of memory? Do the special senses, the perfection and 

 acuteness of which are undeniable, influence the insect's action 

 through a common sensorium, or does each reign independently over 

 those actions of the body to which they stand in special relation* 

 These are questions, a competent discussion of which is only possible 

 when the physiological anatomy of cerebral and sensory ganglia has 

 been thoroughly determined. Finally there remains that faculty 

 which presents itself to difi'erent minds in such different aspects 

 that it would seem scarcely possible for all to agree in discriminating 

 between instinct and reason. 



If, in the foregoing remarks I may seem to have laid myself open 

 to the charge of falling into the vague generalities which I professed 

 at the outset to avoid, I must ask you to bear in mind that I am not 

 setting up any defence of Entomology as a study, but that what I 

 have to say of the anatomy of the cricket necessarily bears on the 

 general characteristics of insect structure, and that any question of 

 physiological interest, arising naturally out of anatomical premisses, 

 falls within the scope of my paper. A preliminary glance over the 

 whole subject is therefore useful in indicating the precise facts 

 which deserve special notice, and also the precise relation in which 

 each fact stands to the general physiology of insect life. 



I conclude these introductory remarks with a few words on the 

 dissection and preparation of the soft parts of insects. 



Much of our knowledge of internal structure has been gained by 

 observation, under the microscope, of insects possessing a transparent 

 integum ent. The larval forms are most suited for such examinations, 

 and are best examined whilst living, when circulation or muscular 

 action is to be studied. If the parts to be studied do not require 

 hardening, it is best to dissect them out immediately after death, 

 glycerine being used to keep them transparent, for when preserved 

 in glycerine the structures can be left to any convenient time for 

 examination. "When spirit is used, hardening occurs in a few days, 



