82 HEREDITY AND SELECTION IN SOCIOLOGY 



and here the Lamarckian theory of use and disuse is inapplic- 

 able. 



A study of the growth of insects shows us that the develop- 

 ment of the cuticle scarcely ever takes place without concurrent 

 small variations of the external membranes, especially of the 

 segments, with their brushes of setae, stings, and so forth. These 

 newly constituted or merely modified membranes, however, are 

 formed or modified before the old protective cuticle is thrown 

 off, and under the protection which it affords. These various 

 membranes must have been formed in a similar manner in the 

 ancestors of the modern insects^that is to say, they were not 

 called into existence by " use or disuse," as the Lamarckian 

 theory maintains ; they arose before there could be any question 

 of their use or functional activity, before the protective cuticle 

 had even laid them bare. The newly formed or modified parts 

 could not have any functional activity until they were already 

 formed or modified. Thus the case of the insects proves the 

 direct contrary of what Lamarckism asserts. 



Similarly, instructive examples of coadaptation in passive 

 organs to which the Lamarckian theory is inapplicable are 

 adduced by Weismann.i If reasoning by analogy be permitted 

 in biological science, we might assert that, if numerous cases of 

 coadaptation and correlated variation can be adduced to which 

 the Lamarckian theory of use and disuse is not applicable, and 

 in which coadaptation must result from another cause than that 

 of functional activity, seeing that the coadapted parts are pre- 

 cluded from entering into activity — at least, during the period 

 of their modification; then it is more than probable that the 

 coadaptation of active parts may also be explained without the 

 aid of the Lamarckian theory. That the gradual development 

 of the muscles, for instance, should have accompanied the 

 gradual development of the antlers of the stag, and have been 

 fiirthered in each individual life by constant use, due to the 

 1 Weismann, Vortrage iiber Deszendenztheorie, ii. 70-75. 



