Mutations and Evolution. 
287 
by the P 5 generation it is fully developed. This is said to he 
accompanied by an increase in the musculature of the arms. The 
development and regeneration of the pad arefound to be independent 
of hormones from the sex organs, since castration of the males 
does not affect it. Also it is said that when F 2 males in which the 
patch had partly developed were crossed with normal Alytes females 
without a patch, a Mendelian result was obtained. This will 
certainly require additional evidence before it can be accepted. 
The fact that in all Anura this pad only becomes apparent 
during the breeding season, seems to indicate that it is of relatively 
recent origin and has not become fully established in thegermplasm. 
It is still in the condition of an organismal rather than a nuclear 
character. Whatever interpretation is put upon these results, as 
indicating a return to ancestral conditions or otherwise, it seems 
difficult to escape the conclusion that functional inheritance has 
taken place in these experiments 1 , even if the gradual transition be 
looked upon as a reversion. Nevertheless, one can scarcely suppose 
that evolutionary adaptation takes place at any such rapid rate. 
It is at any rate an advantage that the subject of inheritance of 
acquired characters is emerging from neglect into the region of critical 
experiment, and the attitude with regard to it is becoming less 
dogmatic and more cautious. Darwin found no difficulty in 
accepting both the Lamarckian and selection factors as contributory 
to evolution. We are endeavouring to show that from the point of 
view of our present knowledge of organic structure the neo- 
Lamarckian and mutation factors are not incompatible or mutually 
exclusive. 
A recent paper which is of interest because it frankly subsumes 
the neo-Lamarckian factor (Roberts, 1919), developes the hypothesis 
that mechanical reaction to stress is the law in all tissues. Just as 
the flying buttresses of a Gothic cathedral were the result of an 
effort to shore up walls which were spreading under the increased 
1 Mac Bride (1919) upholds Kammerer’s contention. Bateson (1919) in a 
reply points out that the fingers in the photograph of the control frog in 
Kammerer’s paper have been clumsily retouched or painted over, and that the 
critical photograph showing the Brunftschwielen of the modified male shows 
what appears to be a sort of excrescence on the outside of the fourth 
finger of the right hand. This, however, does not alter the evidence for the 
presence of a Brunftschwiele, which is clearly shown in the photograph as a 
lump on the right wrist. Moreover, a series of nine histological drawings from 
sections of the horny pad are given, showing the details of structure of this 
region in males of Alytes in which it is wholly or partly developed, also during 
the breeding and resting seasons, and in females. These drawings must 
either be regarded as evidence, in which case they prove Kammerer’s point, or 
treated as deliberate frauds. There seems no sufficient reason for adopting 
the latter alternative, but it is certainly to be expected that Dr. Kammerer 
will now be able to produce specimens showing the horny pad. 
