132 Darwin, and after Darwin. 



is at once felt by the organ ; but that it is indubitably 

 the cause of the now specific and hereditary traits 

 peculiar to normally aquatic, subterranean, and 

 aerial stems, or roots 1 ." 



He continues to furnish other instances in the same 

 line of proof such as the distinctive ' habits" of 

 insectivorous, parasitic, and climbing plants ; the 

 difference in structure between the upper and under 

 sides of horizontal leaves, &c " For here, as in all 

 organs, we discover by experiment how easily the 

 anatomy of plants can be affected by their environ- 

 ment ; and that, as long as the latter is constant, so are 

 the characters of the plants constant and hereditary." 



1 It also serves to show that Weismann's newer doctrine of similar 

 "determinants" occurring both in the germ and in the somatic tissues 

 is a doctrine which cannot be applied to rebut this evidence of the 

 transmission of acquired characters in plants. Therefore even its 

 hypothetical validity as applied by him to explain the seasonal variation 

 of butterflies is rendered in a high degree du'uious. 



[The following letter, contributed by Dr. Hill to Nature, vol. 1. p. 617, 

 may here be quoted. C. LI. M. 



" It may be of interest to your readers to know that two guinea-pigs 

 were born at Oxford a day or two before the death Dr. Romanes, both 

 of which exhibited a well-marked droop of the left upper eye-lid. These 

 guinea-pigs were the offspring of a male and a female guinea-pig in both 

 of which I had produced for Dr. Romanes, some months earlier, a droop 

 of the left upper eyelid by division of the left cervical sympathetic nerve. 

 This result is a corroboration of the series of Brown-Sequard's experi- 

 ments on the inheritance of acquired characteristics. A very large series 

 of such experiments are of course needed to eliminate all sources of error, 

 but this I unfortunately cannot carry out at present, owing to the need of 

 a special farm in the country, for the proper care and breeding of the 

 animals. LEONARD HILL. 



"Physiological Laboratory, Univ. Coll. London, Oct. 18, 1894."] 



