April 5, 1918] 



SCIENCE 



343 



Yale Naval Training Unit for the rest of the 

 year. 



Dr. W. F. G. Swaxn has accepted a profes- 

 sorship in the department of physics at the 

 University of Minnesota, the appointment to 

 take effect on August 1, 191S. 



DISCUSSION AND CORRESPONDENCE 



SCOTT ON THE CANONS OF COMPARATIVE 

 ANATOMY 



Ix a recent number of this journal (N. S., 

 Vol. XLVII., Xo. 1204) my esteemed friend, 

 Dr. D. H. Scott, the distinguished foreign 

 secretary of the Eoyal Society has published 

 a review of my recent volume on " The Anat- 

 omy of Woody Plants." He objects, with de- 

 lightful British vigor, to the Canons of Com- 

 parative Anatomy described in the seventeenth 

 chapter. His criticisms, in fact, of the volume 

 mainly involve these canons, which he re- 

 gards as highly controversial and based on 

 deductive evidence. Dr. Scott naturally has 

 his own opinions on many anatomical sub- 

 jects, and these are often different from my 

 own. The question, however, as to whether 

 the Canons of Comparative Anatomy are de- 

 ductive or inductive appears to be not a mat- 

 ter of opinion but a matter of fact. Induc- 

 tive reasoning, which is ordinarily defined as 

 the drawing of general conclusions from par- 

 ticular facts, was brought into prominence 

 nearly three hundred years ago by Sir Francis 

 Bacon, an eminent Englishman. I must urge 

 that the Doctrine of Conservative Organs is 

 based on purely inductive reasoning. In ac- 

 cordance with that doctrine it is stated that 

 root, leaf and reproductive axis retain an- 

 cestral anatomical features approximately in 

 the order named. This is an induction from 

 the facts that the reproductive axis of the 

 Calamites and Equiseta, the reproductive axis 

 and root of the Araucarian and Abietineous 

 Conifers, the reproductive axis and root of 

 Ginkgo, the reproductive axis and root of the 

 higher Gnetales, all retain notable the features 

 of organization of older or extinct allied forms. 

 It appears to me that Dr. Scott confuses the 

 origin of the Canons of Comparative Anatomy 

 with their application. The Canons are de- 

 rived inductively by the comparison of older 



with modern forms, and are employed deduc- 

 tively to elucidate the relations of modem 

 forms among themselves. 



The soundness of the general principles of 

 the seventeenth chapter of my volume on anat- 

 omy has a very sincere and flattering testi- 

 mony in the attitude of a small coterie of 

 critics of the anatomical work of " Jeffrey and 

 his school."' These critics use the canons in 

 every case, but if I may be forgiven a pvm are 

 imable to aim straight. The most recent in- 

 stance of this defect is furnished by an article 

 on the vessels of Gnetum in the January 

 nimiber of the Botanical Gazette. This author 

 calls attention to the fact that vessels of the 

 lower Ephedra type having end walls with many 

 large open bordered pits are found in the root, 

 reproductive axis, and seedling of Gnetum. 

 He argues very properly from this that the 

 Gnetum type of vessel has come from that 

 found in Ephedra and persists in the conserva- 

 tive organs of the first-named genus. This 

 conclusion is correct as far as it goes, but 

 when the author states that the type of vessel 

 found in Gnetum is different from that found 

 in the Angiosperms he shows a surprising 

 ignorance, since in DeBary's classic text-book 

 of comparative anatomy published over forty 

 years ago a number of cases of angiosperms 

 with the Gnetum type of vessel terminated at 

 either end by a single large-bordered pore 

 have been cited. I might go on to enumerate 

 a number of other equally sincere and flattering 

 testimonials to the soundness of the Canons 

 of Comparative Anatomy, although not to the 

 accuracy of their utilizers, from recently pub- 

 lished works. If imitation is the sineerest 

 flattery, I am indeed flattered. A number of 

 lines of work being carried on in my labora- 

 tory, and among these, notably an investiga- 

 tion on a large amount of material of 

 Comanchean and Laramie Cretaceous Coni- 

 fers, will, I think, add much strength to these 

 generalizations. 



A frank and friendly criticism such as Dr. 



Scott has written always helps to clear up 



differences of opinion by bringing forth clearer 



and more forcible statements from either side. 



E. C. Jeffrey 



