182 THE entomologist's record. 



expansion of the tlieory of intra-selection. The wonderful adaptations 

 which are found in the constituent tissues or pai-ts of an organism were 

 explained by William Roux as due to the application of the principle 

 of selection to the component parts of the organism ; he assumed that, 

 just as we find a struggle for survival among the individuals of a 

 species, so in every organ or tissue the smallest living particles contend 

 with each other, and those that succeed best in obtaining nutriment, 

 being thereby enabled to multiply most rapidly, are victorious over those 

 that are less suitably equipped. Weismann summarises the three factors 

 in the process of selection as " variability, heredity, and struggle for 

 existence." The process of selection may, therefore, go on, not only 

 among individual organisms, but among the different units that go to 

 make np the organism, down even to the smallest conceivable living 

 particles, which Weismann calls " biophors." This process of selection 

 which is carried on in the living parts of organs and tissues is called 

 *' intra-selection." 



In accounting for the process of intra-selection, Weismann is inclined 

 to assume that it is not the " particular adaptive structures which are 

 transmitted, but only the quality of the material from which intra- 

 selection forms these structures anew in every individual life. Pecu- 

 liarities of biopliors and cells are transmitted, and these pecularities 

 may become more and more favourable and adaptive in the course of 

 generations if they are subject to natural selection." From an ento- 

 mological point of view, the statement that " Intra-selection effects the 

 special adaptation of the tissues to special conditions of development in 

 each individual " is interesting, for it is by this means that the occurrence 

 of aberrations, which are so exceedingly abundant among insects, is to 

 be explained. There can be no doubt that intra-selection, like its 

 greater and older namesake natural selection, has, in the course of 

 generations, brought about the greatest possible degree of adaptation 

 and harmony among the different parts of organisms, whicli parts have 

 hence become relatively perfect under the given conditions to which 

 they are normally subjected. Hence a definite form and character are 

 given to the whole and to eacli of its constituent parts, wliilst, at the 

 same time, the mingling of the parental germ-plasms must always secure 

 a certain amount of variation in the primary constituents. 



2. The dauk coloration of Chrysopuanus phloeas in southern 

 LATITUDES. — It bccomes interesting at this stage to consider how far 

 an organism can be affected by external influences to which it is not 

 (according to Weismann) adapted in advance. As an illustration of 

 this, Weismann (p. 22) writes : — " There are numerous examples known 

 in which unusual climatic conditions have produced changes in animals 



and plants A small ruddy-gold butterfly, Polyommatns 



(^Chrysophanus) phloeas, acquires a black tinge when it comes to live in 

 warmer climates, such as that of Southern Italy. This, again, is not to 

 be regarded as an adaptation, but must be looked upon as a direct effect 

 of warmth. This has been shown by Merrifield's experiments, the 

 results of which agree with my own observations. In this and several 

 similar cases there is no ground for supposing that the reaction of the 

 scales of the butterfly is, so to speak, an intentional one — or more 

 correctly, that the determinants of tlie scales were so arranged in 

 advance by natural selection that they should produce black under the 

 influence of a high temperature." 



