l)airs, where its wings can hang straight down, giving thern 

 an occasional shake, until they are fully expanded. This 

 expansion has interested many entomologists, and was dealt 

 with at some length by my friend, and a former member of 

 our Society, Mr. Charles Walker. lie paid considerable 

 attention to it microscopically, and came to the conclusion 

 that the expansion was due to air and fluid. " The 

 nervures," he sa>s, " are pierced in innumerable places by 

 filaments and branched tracheee, spreading all over the 

 adjacent membrane. When expansion takes place, the 

 enclosed trachea^ ser\e for the passage of the air while the 

 fluid is pumped through the unoccupied space between the 

 boundary walls, and the tracheae." Thus it will be observed 

 that Mr. Walker's theory is that the growth depends on 

 fluid being pumped, that is, forced through the membrane. 

 I cannot agree wi#h him. Nature does not use mechanism 

 when natural laws will suffice, and in this case the whole 

 trend of the operation appears to me to point to the natural 

 law of gra\it)-. The position tal<en b}' the insect is 

 significant : the lavish amount of fluid would be unnecessary 

 unless it was there for weight. Then again, what becomes 

 of the pumping apparatus? which, apparently, would only 

 be used for the few moments of development, afterwards 

 to become utterly useless. It was these difficulties, so hard 

 to understand and believe, that made me interested to 

 confirm or refute by experiment ; but the work is great, and 

 I have only touched upon the fringe of this wonderful 

 subject, but sufficient to show that we must not take all that 

 has been written as authentic. Much must be unlearned 

 and much disco\ered before we can say how a moth's 

 wings grow. 



To quote Mr. Walker again, he sa}s : "The general 

 structure of the wings is very similar throughout all orders. 

 They consist of two membranes, united at their edges, and 

 traversed by a series of horny rays which run between them, 

 the upper of which is more strongly attached to them than 

 the lower. These wing rays, or nervures, as we are 



