544 



SCIENCE 



[N. S. Vol. XXV. No. 640 



be content witli the general disclaimer, that it 

 is in the main a criticism of views on vena- 

 tion originating -with the reviewer and not 

 held by myself. 



Probably a combination of the effects of 

 views strongly opposed to those of the author 

 and a very cursory reading of the work re- 

 viewed have brought about the confusion re- 

 sulting in thus attributing to the author much 

 that he has never believed and in giving to the 

 whole presentation a distortion that makes the 

 theory almost unrecognizable. 



Had he read more carefully he would not 

 have failed to have seen, for instance, that the 

 three series under which heads winged insects 

 were discussed, were not presented as natural 

 groups (p. 219), nor that the argument favor- 

 ing the essential identity of tracheated and 

 non-tracheated veins is the conclusion of the 

 argument against the tracheal origin of veins 

 (p. 220), nor have given what I considered as 

 a possible though unwarranted view as being 

 the basis of the system of independents (p. 

 221), nor the small table at the end of the 

 chapter on Lepidoptera as the objective point 

 of the whole work (p. 222), nor a score of 

 other equally evident blunders. 



I desire, however, at this time to criticize 

 the argument offered by the reviewer : " The 

 very presence of tracheae," he writes, " between 

 the two membranes of the wing when they 

 are fusing sufficiently accounts for the pri- 

 mary location of the veins " (p. 220) . The 

 membranes fuse only after the emergence of 

 the insect and the expansion of the wing. 

 The cuticular differentiation of vein and mem- 

 brane either in the wing of an existing insect 

 or in the organ from which the wing was pro- 

 duced in the ancestor of winged insects, is 

 dependent upon changes in the epithelial cells 

 before the deposition of chitin preceding the 

 final molt, and not at the time of the fusing 

 of the membranes. This is simply the way 

 differences of external structure of any part 

 of the body are brought about, not during the 

 molting process, but usually before or possibly 

 rarely during the process of the cuticle deposi- 

 tion which precedes the molt. 



Possibly it may be supposed that he inad- 

 vertently used the word ' membranes ' but in- 



tended to mean the epithelial lining of the 

 wing pad or of the organ which was the 

 precursor of the wing, since in former articles 

 he has described these cell layers as fus- 

 ing. They usually simply touch, however, 

 and often come into no definite organic union. 

 The vein cavities also are so much larger than 

 the tracheaB that it is very hard to see how 

 their presence could have been any determin- 

 ing factor. It is not as though the tracheae 

 mechanically held the epithelial layers apart. 

 Furthermore, why should a longitudinal vein 

 require the presence of a trachea to warn off 

 the approaching epithelial cells, but the cross- 

 veins from the beginning remain capable of 

 looking out for themselves? 



These later suggestions, however, do not 

 represent that author's present point of view, 

 for he is evidently laboring under the delusion 

 that the wing, unlike any other part of the 

 insect's body, expands at the molting time 

 devoid of cuticle and the cells perform this 

 function only after expanding, for he speaks, 

 of the ' differentiation of veins from mem* 

 brane, by the accumulation of cells about the-, 

 vein cavities, and the stretching out of those 

 that lie between' (p. 221). Now as long as 

 the wing remains in the wing pad the veins 

 occupy a very disproportionately large space 

 and the cells of the membrane are correspond- 

 ingly crowded — and in no conceivable sense 

 can they be spoken of as stretching except 

 under the assumption that the wings first ex- 

 pand before these cells are exhausted in cuticle 

 production. 



This absolute failure to appreciate the facts 

 in the ontogeny of the wing, which must also 

 have been true in whatsoever organ the wing 

 may be supposed to originate, this funda- 

 mental misconception is accountable, I believe, 

 for that author clinging so strenuously to the 

 really unsupportable theory of the tracheal 

 origin of veins. 0. W. Woodwo«th 



Univebsity op Califoenia, 

 BEEKEI.ET, March 1, 1907 



DELAYING THE BLOSSOMING OF PEACH TREES BY 

 ETHERIZATION 



As a means of avoiding late spring frosts, 

 the writer finds that the season of blossoming- 



