Weismann's Arguments Against Inheritance 177 



furnishes us itself a proof of this. For from the first 

 impact against the glass partition the inclination con- 

 trary to its instinct must have commenced to arise; 

 nevertheless it effected the replacement of the latter 

 only after a large number of unavailing attempts. 



From all that we have said thus far it follows that 

 it is much to be desired that new and absolutely incon- 

 testable experiments should once for all finally place the 

 inheritance of acquired characters beyond a doubt. But 

 it also follows, as we have said, that if no one of the 

 proofs which we possess already demonstrates this in- 

 heritance in an absolutely certain way, nevertheless all 

 together they supply a great weight of evidence for it. 

 As we shall see later this is true also of indirect proofs; 

 one cannot say of any one of them that it decides the 

 question in one way or the other, but all together 

 they constitute a strong presumption in favor of the 

 Lamarckian theory. 



It will be convenient to examine next the chief argu- 

 ments which Weismann has adduced against this theory. 

 They can be reduced in substance to the following: 



i. "In many animals," he writes, "for instance in 

 many insects, instincts appear which are exercised only 

 once during life. It is sufficient to cite the laying of 

 eggs by ephemerids and many butterflies, the conjugation 

 of bees, the search for proper hiding places in which 

 caterpillars may change into chrysalids, one species 

 suspends itself, another lying on the ground builds de- 

 fences, a third goes deep into the earth, a fourth spins 

 itself a case in a rolled up leaf, and so on, and so on. 

 Further there belong here the several species of cocoons 

 which some butterflies, especially the bombycids, spin 

 in a fashion so astonishingly complicated and so well 



