174 NATURAL SCIENCE. „^,, 



aerial parts of plants. Similarly, the tubers of the potato, a specific 

 character, as the name Solanum tuhevosum implies, can be made to 

 appear on the upper part of the plant, by not allowing them to grow 

 underground. Lilies will sometimes develop bulbils on their stems 

 abnormally, just as Lilium hiilbifcrum normally produces them. All 

 such, and many other cases that might be mentioned, appear to 

 indicate that if germ-plasm be requisite for the development of here- 

 ditary characters, it must be present practically everywhere, and in 

 readiness to produce them when called upon to respond to external 

 intiuences which give rise to them. 



Hence we arrive at the necessity of extending Dr. Weismann's 

 hypothesis and, adopting his own words, to say : " That all somatic 

 nuclei of plants may contain a small amount of unchanged germ- 

 plasm " (p. 21 i). 



2. Acquired Characters are not Hereditary. 



Dr. Weismann defines them as being " those characters which 

 have been acquired by the influence of special external conditions 

 during the life-time of the parent; such cannot be transmitted at all " 

 (p. 267). " They cannot produce any effect in the transformation of 

 the species, simply because they can never reach the germ-cells from 

 which the succeeding generation arises" (p. 388). Acquired charac- 

 ters he considers to be such as are attributable to " use and disuse, 

 practice or neglect, nutrition, light, moisture, and climate" (pp. 387, 8). 

 On the other hand, he asserts that " changes in the germ-plasm are 

 the first results of the new conditions " (p. 414). 



Thus, in the case of wild carrots cultivated by Hoffman, in 

 which changes produced by cultivation in the structure of the root 

 were hereditary, Dr. Weismann observes: — "It is sufficiently 

 obvious that in this case we are also concerned with a change which 

 did not become visible until after some generations had elapsed, and 

 which was therefore a change in the germ-plasm " (p. 414). 



It would seem not unreasonable to demur to his supposed 

 necessity of the e^eci being visible at first, for it is (juite conceivable, 

 and indeed probable, that time may be required in most cases for 

 the influences of the environment to accumulate in order to produce 

 any marked effects. Moreover, although no changes may be exter- 

 nally visible for two or more generations, yet the effects may be 

 recorded in some alterations in the tissues only observable by the 

 microscope, and are potentially accumulating until at last they 

 become very manifest to the naked eye. Indeed, no one, probably, 

 has as yet actually examined the roots microscopically with the 

 express purpose of testing this point, for the attention of botanists 

 has not been brought to it before. 



In the case, however, of certain experiments conducted by the 

 late Professor J. Buckman witli parsnips and carrots, the change was 



