186 



THE ENTOMOLOGIST. 



how comes it that even in the South of Ireland, with a climate 

 more southern than its latitude represents, no reversion to 

 the tji^e has taken place in the lapse of cycles of centuries ? 

 The variation acquired under pressure of the environment has 

 apparently so impressed itself on the organism that suc- 

 ceeding ages of pre-glacial climate have not erased the here- 

 ditary traits. 



The phenomenon probably would not have been displayed if 

 isolation had not segregated the variety in these islands from 

 admixture with the lowland continental type. It is of course, 

 however, open to discussion whether the alpine form or the 

 so-called type is the more primitive one. In either case, however, 

 we seem to have an instance of the persistence of acquired 

 characters. On the other hand, as above remarked, melanic 

 variations are credibly asserted to be rapidly developing in 

 smoky districts. These and similar facts require careful investi- 

 gation, and students of such phenomena should carefully try to 

 distinguish what appears to be a hereditary and constitutional 

 bias, giving rise (often sporadically) to fixed types of variation, 

 whether sexual or otherwise, such as the var. valcsina oiArgyimis 

 liapliia, and the named ones of Apamea oculea, from such oc- 

 casional topomorphic forms whose origin may be traced to local 

 influences. 



In referring, however, to the views of Professor Weismann 

 and Mr. Herbert Spencer, Mr. Sharp gives a very inadequate and 

 therefore misleading analysis of the theories under discussion 

 lately in the * Contemporary Keview.' Inadvertently, doubtless, 

 he summarises the German biologist's thesis thus baldly : — 

 "All specialized forms are the result of the pressure of the 

 environment acting through heredity"; while "acquired vari- 

 ations are not transmitted." It seems unfortunate that so 

 incomplete a definition of the very abstruse speculations of 

 the celebrated author should have been put forward without 

 qualification or explanation. To a reader ignorant of the sub- 

 ject, it seems a contradiction of terms to speak of heritable 

 varieties, if variations are not transmissible. Of course Mr. 

 Sharp's reference to the subject is a merely passing one, but it 

 conveys an inaccurate impression of the real issue. Professor 

 Weismann, whose essay is styled "The All- sufficiency of Natural 

 Selection," contends that modifications of structure arise from 

 fortuitous variations of germinal products, uninfluenced either 

 by the action of the environment, or by functional use or disuse, 

 but springing solely from constitutional tendencies of the parents 

 not immediately referable to any assignable stress of external 

 influences. These chance variations of offspring are pruned by 

 natural selection, which secures the survival of the fittest. Tha 

 English philosopher, on the other hand, contends in favour of 

 the Lamarkian principle of the heritability of variations arising 



