THE VARIATION OP THE IMAGINES OP THE LEPlDOPTERA. 71 



at length, the details of this theory as to the origin of the protective 

 coloration of the leaf-butterflies of the genus Kallima. We consider 

 that the response to environment, as exemplified by the form, colour, 

 shape, etc., of insects, is the outward expression of certain variable 

 factors, which, arising within the organism, are directed as to what 

 exact lines they shall ultimately take by the external conditions of life, 

 i.e., by utility. Weismann asserts that selection and utility originate 

 the colour-patterns, which is true so far, and only so far, that actual 

 colour-patterns do not exist until natural selection forms them out of 

 the crude material at its disposal. It appears to us that there are two 

 processes of selection engaged, before the ultimate production of any 

 colour-pattern — (1) Selection (internal) among the biophors them- 

 selves, and dependent on the vital processes. (2) Natural selection 

 (external), by means of which the variously coloured scales are formed 

 into a pattern useful to the insect. The scale determinants, it seems, 

 are subject to the same physiological laws as those of other organs. 

 They are guided in the course of their development by various con- 

 siderations, and whilst their general characters are due to internal 

 forces, the special peculiarities of their arrangement are determined 

 by natural selection ; the particular variable factors which are useful 

 for the preservation of the species being chosen for the purpose of 

 building up the required patterns. 



The fundamental difference (apart from detail) between the old 

 conception of selection, and that more recently propounded by Weis- 

 mann, is that by Darwin, variations were considered to be fortuitous, 

 and that selection had to wait for one of these chance occasions to 

 occur, whilst Weismann considers that every portion of the organism 

 contains within itself, from the first, an indefinite number of varia- 

 tions, some of which are almost sure to be in the direction required. 

 Selection chooses those required, and, by the process of intra-selec- 

 tion, compels them, as it were, to overcome their competitors, and 

 utilises them to produce those results which shall be of service to the 

 organism. 



At present, however, we have not got to the all-important factor 

 in the study of variation, viz., what are the physiological factors that 

 decide which of Weismann's theoretical " determinants " shall be 

 developed, and which be extinguished. Weismann tells us that, even 

 in the germ, every part of an insect — a wing or a scale — however 

 large or small, is composed of theoretical molecules called " determi- 

 nants." These, by intra-selection, i.e., by the competition of the 

 molecules themselves, become non-existent as one absorbs the other, 

 the predominant " determinant " finally deciding the nature and 

 character of the part. He, therefore, considers that the particular form 

 of the part, say a scale, is determined at a comparatively early stage of 

 the insect's existence, i.e., once the predominance of a particular 

 " determinant " is assured. 



Although the assumption of " determinants " enables us to explain 

 certain phenomena, it does not bring us any nearer to the actual physio- 

 logical activities which result in variation, nor does it explain to us how 

 certain external factors result in variation. To say that a scale of an 

 insect originally has in it the potentialities of becoming white, 

 yellow or red, and that when the scale finally emerges red, to explain 

 it by saying that the red " determinant " was successful over the white 



