104 (May, 



Now, the more minutely we investigate and classify our insects, the 

 more commonly do we come upon instances in which the only coarse 

 and tangible characters by which one species may be distinguished with 

 certainty from another closely allied to it, lie in these secondary sexual 

 structures ; in fact the structures constitute for us the specific charac- 

 ters. Hence the conclusion seems inevitable that many of the characters 

 that go to form a species have their start in some primary change in 

 the reproductive glands, and that these organs are not merely passive 

 agents concerned in the nourishment of the germ-matter, but do them- 

 selves take an active and creative part in the genesis of species. 



Be this as it may, no doubt exists of the close relationship 

 between the primary and secondary organs, and the question arises, 

 by what means or through what channel is it eifected ? Probably 

 the answer would be that it is due to the agency of the nervous 

 system. Some stimulus or impression, so it is affirmed, is conveyed 

 from the reproductive glands to that part of the nervous system pre- 

 siding over the development, say of the claspers, in consequence of 

 which the latter take on their proper growth and form. At one time 

 no other explanation was perha2:)s possible, but recently there has 

 been brought to light a singular and quite unsuspected function 

 possessed by many, if not all, of the glands of the body. In addition 

 to their ordinary secretions, which find their way into the ducts, and 

 may, therefore, be called external, it is now recognised that they 

 produce what are known as internal secretions— secretions which 

 pass back at once into the blood, where they probably act as highly 

 specialized foods necessary to the well-being of the organism. As at 

 present taught, this applies only to the daily wear and tear of the 

 body as a going concern, but I see no reason against a wider applica- 

 tion of the principle, and why may we not suppose that in the building 

 up of the structures one part may produce a substance which serves as 

 an essential element in the nutrition of some other part, and without 

 which it could not take up its true and proper development. Thus, 

 in place of a nerve-bond between two correlated parts, it is [jossible 

 to substitute a food-bond, or, in other words, a chemical one. It may 

 be mere speculation, yet it is in this direction, in the application of 

 chemistry to vital processes, that most hope lies of penetrating some 

 of the mysteries of organic life, nor are considerations altogether 

 wanting in support of it. To revert to the illustration already bor- 

 rowed from the stag : if the influence be purely nervous, as is 

 commonly believed, the path by which it is conveyed all the way from 

 the testes to the horns over the intricate and interlacing: lines of the 



