xn 



the greater dryness of Eastern Java as compared with the western portion of 

 that island, an undoubted fact in itself but of no such importance as has been 

 attributed to it in this manner. Such superficial treatment, however usual it 

 may be, has, in my opinion, as little in common with serious science as have 

 the many so-called historical novels of Alexandre Dumas with the actual history 

 of France, although many people, without scientific education and decidedly 

 without scientific critical faculty, consider it as such in good faith and judge 

 by that criterion. It should not, however, be inferred from this that I absolutely 

 deny that specific influences can bring about such changes. I certainly do not, 

 for instance, deny that the greater or lesser degree of salinity of sea-water 

 exercises influence on the morphology of fishes and other marine animals. 

 Providing these influences are, however, apprehended in a scientific manner 

 and are understood to be factors which, in the course of the natural evolutionary 

 processes of form or colour, to which such species are normally subject, act as 

 stimuli, causing some retardation or acceleration in them or conducting this 

 course in a specific direction, and providing it be understood that this action on 

 the individuals is mainly governed by their individual susceptibility which 

 may vary in a high degree. For susceptibility is a quality, whose nature is 

 indeed very little known to us, but whose existence cannot be denied. No 

 stimulus, of whatever nature, can exercise influence unless the susceptibility for 

 it is present ; where this is not present originally it appears, nevertheless, that 

 where the individual has been exposed to this stimulus for a period, this quality 

 may even be generated. The requisite period again varies considerably in 

 duration and may certainly in some cases be of very great length. 



Many experiments have been conducted in which especially pupae of Lepi- 

 doptera have been exposed for periods of greater or lesser duration to varying 

 degrees of heat or cold ; the most extensive and important are those carried 

 out b)' Dr. E. Fischer {Allgemeine Zeitschriji fiir Enlomo/ogie, VI n°. 20) and 

 latterly by Dr. Harry Federley. It was observed that in consequence the 

 imagines developed from these pupae exhibited differences in colour and some- 

 times in form from imagines developed under normal conditions, and owing to 

 the existing ignorance, to be discussed further presently, with regard to the 

 nature of the evolutionary changes to which Lepidoptera are subject and 

 especially concerning the nature of colour evolution, these colour modifications 

 were assumed to be due to the direct chemico-physical action of the said heat 

 or cold. The usual superficial reasoning relying upon this would, therefore, 

 attribute the production of colours in Lepidoptera — and even in animals 

 generally — to such direct climatic influences and this erroneous conception 

 has still many adherents. The fashion, alluded to, of referring each deviation 



