481 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



explanation must be sought in an hypothesis constructed on the lines 

 of pangenesis." * 



On the other hand, he says that : " If the transmission of acquired 

 characters were proved to be an undoubted fact, Weismann's hypothesis 

 of heredity would inevitably collapse." t 



The author observes : " The apparently hereditary effects of disuse 

 are more probably due to the cessation of Natural Selection, which can no 

 longer maintain the efficiency of a useless part." ± But why may not the 

 degeneration, say, of the toes of the cow and horse be due to the decreased 

 flow of blood for many generations until the organ has atrophied, and 

 so become hereditary ? This, as a theory, is far simpler than that myriads 

 of cows and horses born should die, leaving only those with enlarged central 

 toes suitable for habits of life. Or why may not the poiver to produce them 

 cease, as well as the organ itself degenerate ? Rudimentary organs in both 

 kingdoms are innumerable and obviously not wanted ; so that induction, 

 or the " accumulation of probabilities," sufficiently establishes the belief 

 in the effect of use and disuse being hereditary. 



Professor Poulton is evidently not aware of the vast number of proofs 

 of the heredity of acquired characters in plants. 



The present writer would suggest that it is not only the details of the 

 material machinery (the structure of nuclei) to which we must look, but 

 also to the forces at work in building up an organism. No known force 

 can direct itself ; it remains potential until something, not itself, sets it 

 going. E.g. a batsman drives the ball between two of the opposing field ; 

 the force resides in his muscles, but the direction of the force is from a 

 totally different source — his mind. Now, the structure of animals and 

 plants depends entirely upon physical matter and force ; but the latter 

 " drives " the former in innumerable directions ; so that lime is sent 

 to the bones, silica to the teeth, salt to the tears, &c. ; while elements 

 are made to combine in scores of places specially localized for their 

 compounds, as bile. 



What directs all these physical forces, which in turn act upon matter ? 



Professor A. H. Church, F.R.S., finding that he can make many 

 "organic" substances in his laboratory, asks the question: "What 

 takes my place in the plant or animal which makes precisely the same 

 products ? " 



It is quite certain that the elements cannot make compounds located in 

 definite places ; so he calls this remarkable feature of life " directivity." 



It appears — e.g. in the result of a direct response to external action- - 

 that the Virginia creeper at once develops adhesive pads at the tips of its 

 tendrils as soon as contact with a rough wall is "felt." Such are not 

 hereditary, but have to be made only by contact ; but the Japanese 

 species now prepares the pads in anticipation of contact, but only com- 

 pletes them after it. Such, then, are an hereditary acquired character. 



This idea of directivity will have to be reckoned with in future theories 

 of heredity and evolution. 



Essay VI. contains "A Remarkable Anticipation of Modern Views 

 on Evolution," by J. C. Prichard, whose " Researches into the Physical 



* Essays, p. 126. t L»r. tit p. 132. J Loc. rit. pp. 137, 138. 



