Febeuaey 11, 1898.] 



SCIENCE. 



195 



Pierre Fish, Cornell University ; Miss Cath- 

 arine Foot, Evanston, 111.; Mrs. S. P. Gage, 

 Cornell University ; Professor S. H. Gage, 

 •Cornell University ; Professor C. W. Har- 

 gitt, Syracuse University ; Dr. B. F. Kings- 

 bury, Cornell University ; Professor E. W. 

 McBride, McGill University; Dr. P. C. 

 Mensch, Ursinus College; and Professor A. 

 D. Morrill, Hamilton College. 



The follovFing papers were presented and 

 tliscussed : 



On Reading the Records of Evolution in the 

 Wings of Insects. J. H. Comstock. 

 This was an illustration of a method of 

 taxonomic work outlined by the v/riter sev- 

 eral years ago in an essay entitled ' Evolution 

 and Taxonomy,' where he urged a more con- 

 stant use of the theory of evolution than is 

 customary in work of this kind. It was 

 suggested that, as the structure of a highly 

 organized animal or plant is too complicated 

 to be understood in detail at once, the stu- 

 dent begin with the study of a single organ 

 possessed by the members of the group to 

 be classified, and determine its primitive 

 form and the various ways in which this 

 has been modified. The data thus obtained 

 will aid in making a provisional classifica- 

 tion of the group, which should be con- 

 firmed or corrected by a similar study of 

 other organs. 



The illustration given in this paper was 

 an efforb to obtain data bearing on the 

 working-out of the pbylogeny of the orders 

 of winged insects, by a study of the char- 

 acters presented by the venation of the 

 wings, the homologies of the anlagen of the 

 winged-veins, i. e., the tracheae that pre- 

 cede them in nymphs or pupse, were de- 

 termined, and a hypothetical type repre- 

 senting the arrangement of the trachese in 

 the nymph of the stem form of winged in- 

 sects was figured. It was then shown how 

 this type has been modified in the different 

 lines of descent ; in some by a reduction 



in the number of wing-veins by a coales- 

 cence of adjacent veins ; in others by the 

 development secondarily of supernumary 

 veins. Each of these processes can be ob- 

 served by a study of the ontogeny of cer- 

 tain species representing the line of devel- 

 opment in which it occurs, and also by a 

 study of allied forms in which it has taken 

 place in varying degrees. 



The Records of Evolution in the Wings of 

 Dragon-Flies. J. G. Needham. 

 This paper furnished a concrete illustra- 

 tion of the method outlined in the preced- 

 ing one. The adult dragon-fly wing was 

 compared with the typical insect wing and 

 was seen to differ widely from it, but the 

 arrangement of the tracheae in the bud- 

 ding wing of a young nymph was shown 

 to be nearly that of the type. The devel- 

 opment of the complex adult venation was 

 then traced in the development of the 

 trachefe of the nymph, and it was seen 

 that these trachete show what was the 

 primitive condition of every feature of 

 the venation. 



The triangle was selected for an illustra- 

 tion of the reading of the dragon-fly record, 

 and it was shown that primitively this dif- 

 fered little from an ordinary rectangular 

 oreole, while with the adaptation of it to the 

 bracing of the basal part of the wing every 

 part of it has been modified along certain 

 definite lines, which can be clearly traced. 

 Some of these lines of development were 

 illustrated by series of figures. It is stated 

 that the triangle is but one of many corre- 

 lated wing characters, that specialization 

 has taken place along many different lines, 

 and that almost every wing has preserved 

 in some of its parts a bit of the ancestral 

 record. In conclusion, attention was called 

 to the greater value of conclusions based on 

 a true genealogic study of a single organ 

 than of those based on the mere assortment 

 of characters at large. 



