36 



SCIENCE. 



[N. S. Vol. XXII. No. 550. 



studies bear the stamp of repetition and 

 •complement, from which the stimulus of 

 newness is wanting, or they are carried on 

 upon materials which are very difficult to 

 ■obtain. The constructions of the idealistic 

 morphology, however, often proved to be 

 untenable. 



But the first experiments towards a 

 causal morphology, brought disillusion. 

 For only a short time lived the hope of 

 being able to answer, e. g., the question as 

 to the arrangement of leaves through the 

 effect of mechanical factors, or to refer the 

 form-relations of a plant to the direct in- 

 fluences of gravity and light on the plant. 

 It soon became evident, however, that such 

 involved problems are not to be unraveled 

 by such simple means, and this may well 

 have resulted in the suppression of interest 

 in morphology. 



At this point phylogenetic morphology 

 appeared to take on a new lease of life. 

 This, however, in natural science is con- 

 nected, on the one hand, with the appear- 

 ance of a new, creative ( ? ) idea, and, on 

 the other hand, with the discovery of new 

 methods. Now the theory of descent has 

 powerfully stimulated morphological re- 

 search. But has it brought to it, as, e. g., 

 Strasburger has held, a new method, the 

 phylogenetic? Alexander Braun has al- 

 ready properly answered this question in 

 the negative. 



Scott, also, has maintained that historical 

 morphology (as regards both living and 

 fossil plants) is dependent upon compara- 

 tive study, that is, makes use of the same 

 method as was in evidence before the ap- 

 pearance of the theory of descent; indeed, 

 the most important homologies in the plant 

 kingdom became known through Hofmeis- 

 ter at a time when the idea of descent was 

 far from that general acceptation which it 

 at first gained through the life work of 

 Darwin. 



The method has then from first to last 



remained the same : the most comprehen- 

 sive comparison not only of mature forms, 

 but also their development. A special 

 ' phylogenetic method ' there is not, but only 

 a phylogenetic conception of morphological 

 problems. These are, however, just as at 

 first was the case with idealistic morphol- 

 ogy, purely formal. Modern morphology, 

 in my sense, however, differs from the 

 older in this, that it goes beyond the method 

 of mere comparison. It allows the setting 

 up of genetic trees to rest for the while, 

 since, with our present knowledge, this 

 meets with insuperable difficulties and has 

 brought almost as much disappointment as 

 the idealistic morphology. For just this 

 reason, namely, because we are persuaded 

 that no other forces have been at work dur- 

 ing the phylogenetic history than those 

 which now control the development of each 

 particular organism, do we wish, first of 

 all, more exactly to learn what these are. 

 We are concerned not alone with the de- 

 termination of the single successive stages 

 of development. These must, of course, be 

 followed, but in addition we should follow 

 all phenomena which may be got at by our 

 means of observation, whether directly, by 

 the microscope, or by chemical analysis. 

 We may, therefore, say: The basal prob- 

 lem of the present day morphology is not 

 phylogenetic development, but development 

 in general. "We must, therefore, take our 

 departure from the investigation of indi- 

 vidual development (of ontogeny), for 

 only this lies before us complete and with- 

 out any break, and further, because the 

 study of ontogeny only may proceed from 

 the experimental point of view. An un- 

 derstanding of development is possible only 

 when the conclusions, to which the observa- 

 tion of the phenomena of development has 

 led us, rest upon experimental proof; in 

 other words, when we ask questions of 

 Nature, and obtain our answers to them. 

 Every little step— and with such only 



