82 fHE ENTOMOLOGIST S RECORfl. 



depend on its producing structures that are directly transmissible — it 

 cannot do that — but rather consists in its causing a development of the 

 germ-structure acquired by the selection of individiials, which will be 

 suitable to varying conditions. Intra-selection effects the special 

 adaptation of the tissues to special conditions of development in each 

 individual." 



Weismann further points out that the increased development of 

 certain organs or parts is of necessity accompanied by secondary 

 modifications in other organs or parts connected therewith. Instancing 

 the increased strength of the skull, muscles and ligaments of the neck, 

 contemporaneously with the increased growth and weight of a deer's 

 antlers, he does not think it at all necessary that all the parts concerned 

 should simultaneously adapt themselves by variation of the (jerm, to 

 the increase in size of the antlers, because in " each separate individual 

 the necessary adaptation will be temporarily accomplished by intra- 

 selection under the trophic influence of functional stimulus." It is a 

 little difficiilt to follow this ; for if modification of these tissues once 

 sets in, even as a result of intra-selection, as suggested by the Professor, 

 one fails to understand why the peculiar qualities of these structures 

 should not, according to his own view, be transmitted with the peculiar 

 qualities Avhich result in the production of the enlarged antlers. He 

 further suggests that the " discord among parts may sometimes be such 



that intra-selection is not able to produce harmony but 



that the secondary adaptations would probably, as a rule, keep pace 

 with primary variations," and that in " the course of generations, by 

 the constant selection of those germs, the primary constituents of 

 which are best suited to one another, the greatest possible degree of 

 harmony may be reached"; further, that "the mingling of the 

 moieties of parental germ-plasm in fertilisation must be of the utmost 

 importance in this connection, for they secure the constant presence of 

 an abundance of very varied combinations of primary constituents," 

 whilst " a complete harmony of the primary constituents can therefore 

 never exist in the germ-plasm of sexually produced individuals ; for 

 this germ-plasm is always composed of two individually distinct 



halves and it follows that in every act of fertilisation 



very different primary constituents of corresponding parts, derived 



from both father and mother, must meet in the germ the 



primary constituents of their germ substance could not be united 

 together to produce a young organism, exhibiting harmony in its 

 various parts, if they did not all have a certain scope for variation, so 

 as to render them capable of adaptation to one another." One other 

 statement must be considered, viz., that " the supposition of the 

 whole activity of intra-selection presupposes the specific sensitiveness 

 of the various primary constituents, and of the units of smaller or 

 larger groups of these, and this sensitiveness can naturally only have 

 arisen through ordinary selection of individuals owing to the variation 

 of the germ." 



Having considered these general principles bearing on intra- 

 selection, Weismann argues that the " differentiation of sex can also, 

 within certain limits, be regarded from a similar point of view." In 

 dealing with this part of his subject, Weismann selects, among others, 

 the social insects — ants, wasps, bees and termites- — in which, as all 

 my hearers are aware, sex is somewhat complicated, and in which there 



