XV A CRITIC OF NATURAL SELECTION ANSWERED 307 



the excellence of our milking cows and goats may be 

 attributed partly to selection and "partly to the inherited 

 effect of the increased action, through mans art, of the secret- 

 ing glands'' and he adds, " This fact " is strictly analogous 

 to what takes place in the vegetable kingdom ! Here we 

 have a mere opinion of Darwin's, nowhere supported by 

 direct observation or experiment and now seriously chal- 

 lenged by a large body of naturalists, set forth as " a fact." 

 Again, at page 157, the case of the various " ant-plants " 

 of the eastern tropics is referred to, and it is stated that 

 Dr. Beccari explains the curious hollow stem in which the 

 ants dwell as partly due to the irritation of the ants 

 inducing hypertrophy of the vegetable tissue, which '' then 

 becomes hereditary " ; and Mr. Henslow concludes that 

 there is abundant evidence to prove that many organs of a 

 plant, if subjected to irritation, can become materially 

 altered and develop new processes, and, " secondly, that 

 these altered states, if the irritation be persisted in, may 

 become hereditary." Here again are only opinions with- 

 out a particle of proof; and I can find nothing more to 

 the point in the whole volume. The case of galls is very 

 briefly referred to at p. 144, and their non-heredity is 

 passed by with the remark that the predisposition to pro- 

 duce them may be greater now than formerly, and that 

 the galls themselves may be larger than they were at 

 first. But surely if the effects of insect irritation are 

 anywhere hereditary it would be here. An oak tree which 

 lives several hundred years is subject to this irritation in 

 greater or less degree almost every year, and the irritation 

 itself is not momentary and intermittent, as in the case 

 of insects visiting flowers, but is kept up by the presence 

 of the Qgg and growing larva during a considerable por- 

 tion of the period of active vegetable growth, and this has 

 been going on for thousands, probably millions, of years. 

 Yet neither do oaks nor any other plants produce galls 

 spontaneously, as they certainly should do if the results of 

 irritations are in any general sense hereditary. This 

 seems to me to be a really crucial experiment continually 

 repeated by nature. 



I may here remark that Mr. Henslow's theory utterly 



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