808 THE ENTOMOLOGIST. 



zatima of S. luhricipeda, seem to be cases in point. Let us 

 eliminate such forms and put them into a group by themselves ; 

 with their known British and Continental distribution, if in any- 

 way they are restricted to locality. Carefully compiled lists 

 of melanic variations, found in particular districts peculiar in 

 their physical or other characters, would be of much avail also 

 for students of the subject. That some more precise information 

 is desirable appears to me probable, for I observe almost every 

 writer, Mr. Sharp included, refers to the Irish lepidopterous 

 fauna as being melanic or melanochroic in its general tendency. 

 Mr. Tutt invariably attributes this character to the Sligo neigh- 

 bourhood in particular, a district better represented perhaps in 

 English cabinets than any other Irish one, through the industry 

 of Mr. Russ. Nevertheless I find, by a recent correspondence with 

 that gentleman, that he agrees with me, who have also collected 

 largely there, in denying that the Sligo Macro-Lepidoptera 

 present any predominant melanic facies. And as a result of a 

 good many years of work in widespread localities in Ireland, I 

 would venture to enter a caveat against any conclusion that the 

 Irish fauna generally is so characterised. I hope to point out in 

 the Irish Catalogue, now being published, the range of variation 

 of each species so far as ascertained. Specialists will then be in 

 a better position to institute juster comparisons between our island 

 fauna and that of wider areas. Would it be too much to hope 

 that Mr. Tutt, with his fine collection, extensive correspondence, 

 and indefatigable industry, will sooner or later tabulate the facts 

 we desire to discuss, and define a little more exactly the 

 phenomena certainly ascertained ? His "Variation of the 

 Noctuse " does not deal as fully as is desirable with the geo- 

 graphical distribution of the principal melanic varieties. 



Mr. Sharp has pointed out that in the discussion of the 

 subject, biological doctrines and terms have been somewhat 

 loosely and confusedly invoked. As there are many entomo- 

 logical workers who have not studied the points at issue, I may 

 be pardoned for stating concisely the chief conclusions at which 

 zoologists have arrived with regard to the agencies at work. In 

 reference to varieties the three primary agents supposed to 

 evolve variations are : — 1. The immediate action of the environ- 

 ment, i.e., humidity, food, temperature. &c. 2. Constitutional 

 or congenital tendencies. 3. Change of function, or the exercise 

 or disuse of organs. In reference to species, the secondary 

 factors operating to crystallise variations into species appear to 

 be as follows : — If they are transmissible (for the heritable 

 nature of the first and third classes of variations is denied by 

 many of our most eminent authorities), (1) accumulation may 

 perpetuate them as environmental and functional modifications of 

 species respectively. With regard to the second class, or constitu- 

 tional variations, since they are undoubtedly heritable, either (2) 



