May 20, 1898.] 



SCIENCE. 



701 



theory at a time when the cautious De Bary 

 (in his criticisms of the second editions of 

 the ' Text-book ' ) looked askance at it. The 

 Archegoniates are treated in the ' Text- 

 book ' with special interest, forming part, as 

 they had done, of his own researches. His 

 grouping of thallophytes (in the fourth 

 edition of the ' Text-book ') , which met with 

 such adverse criticism, has at any rate at- 

 tained the satisfactory position of being 

 approached again in our own days by many 

 writers. 



Throughout his life he cared little for 

 those details that oftea fill men's lives, and 

 preferred to view matters from a wide and 

 general standpoint. In the first edition of 

 his ' Text-book ' he had set his face against 

 ' idealistic morphology ' at a time when it 

 was dominant, and in a paragraph of his 

 'History ' that promises to become classical 

 he laid bare the foundations upon which 

 this tendency rested. 



Darwinism was another bugbear to him 

 and he intended to attack it vigorously in 

 the ' Principles.' " As far as it goes I am 

 delighted to be free from ' the immutability 

 of species ' and to be able on good grounds 

 to accept evolution. But it is absolutely 

 uncertain how we are to conceive of this 

 latter. Therefore, I say that the natural 

 system of classification is only to be ex- 

 plained by descent, but how this is to be 

 explained no one knows. I regard descent 

 as a fact, like gravitation, about which also 

 we are absolutely in the dark." His whole 

 conception of the world rebelled against 

 ' the crude materialism ' which he thought 

 he found in Darwinism. "If my 'Princi- 

 ples ' do not meet with the response I had 

 expected, they have done me good service in 

 showing me that Darwinism as a whole is 

 entirely superfiuous for any scheme of the 

 final causes of nature. A superfluous theory 

 has received its sentence." 



He sought, however, to obtain some simi- 

 lar conception of causes by his theorj' of 



' organ- forming matter,' which caused the 

 external diversity of organs to appear de- 

 pendent upon their material differences of 

 substance, a view which had its origin in 

 the researches alluded to above on the de- 

 pendence of bud-formation upon the as- 

 similation activity of the leaves. By this 

 a theoretical basis was gained for experi- 

 mental morphology ; deformities, galls, etc., 

 could be referred to definite changes of sub- 

 stance ; and the assumption that stem- 

 forming substances find their way to the 

 point of stem-growth, root-forming to that 

 of the root-system, explained to him most 

 naturally the facts to be seen in reproduc- 

 tion. It is evident that in such a difficult 

 subject one must look for sketches, or gen- 

 eral views, rather than theories worked out 

 in detail. But at any rate Sachs' views are 

 more fruitful than Nageli's ' Idio-plasma,' 

 and he made a number of experimental 

 morphological studies on their bases. 



He had already arrived at the conception 

 of the continuity of the embryonic sub- 

 stance before the appearancq of Weis- 

 mann's 'Germ-plasm.' "That which has 

 maintained itself alive, and has continually 

 reproduced itself since the beginning of or- 

 ganic life upon the earth, moving steadily 

 onward in the eternal change of all struc- 

 tures, in the unvarying alternation of life 

 and death, that is the embryonic matter of 

 vegetation, and it is this which in certain 

 cases differentiates itself into the two sexes 

 in order again to unite." 



He conceived of the multiplicity of plant 

 forms as arising, on the one hand, from the 

 phylogenetic morphological differentiation 

 (this, however, he regarded as an ' absolute 

 mystery'), and on the other from the re- 

 action of the common vegetable substance 

 in response to external stimuli (automor- 

 phosis and mechanomorphosis). ' Adapta- 

 tion ' in Darwin's sense of the expression 

 he considered entirely superfluous, and 

 herein he was in entire agreement with 



