August 20, 1009] 



SCIENCE 



243 



of resemblance of cliildren to fathers rests 

 more on mathematical ideas than on biological 

 indications, to judge from Thompson's ac- 

 count of it. To show that later children re- 

 semble their fathers more than earlier chil- 

 dren would not demonstrate a cumulative 

 paternal influence, but might only mean that 

 children of older parents have less tendency 

 to vary from parental characters than children 

 of young parents. It would still be necessary 

 to show that the paternal resemblances of the 

 later children increase more than their ma- 

 ternal resemblances. O. F. Cook 

 Washington, 

 April 30, 1909 



SCIENTIFIC BOOKS 

 A Comparative Study of the Thorax in 



Orthoptera, Euplexoptera and Coleoptera. 



By K. E. Snodgrass. Proc. Ent. Soc. 



Washington, IX., 1908, pp. 95-108, pis. II.- 



V. 

 The Thoracic Tergum of Insects. By E. E. 



Snodgkass. Ent. News, March, 1909, pp. 



97-104, pi. VI. 

 The Thorax of Insects and the Articulation 



of the Witigs. B. E. E. Snodgrass, of the 



Bureau of Entomology, U. S. Department 



of Agriculture. No. 1687 — Proceedings F. 



S. National Museum, Vol. XXXVI., pp. 



511-595, with plates 40-69. Published June 



18, 1909. 



The series of memoirs, under the above 

 titles, constitutes a very valuable addition to 

 the literature of insect structure. The last 

 paper contains the detailed evidence for the 

 theories presented by the other two and is 

 really considerably broader than the title indi- 

 cates, including an elaborate discussion of the 

 segmentation of the head and abdomen and is 

 not limited to a study of adult structure. 



The diagrams (Figs. 1-6) present in an 

 extremely satisfactory manner the author's 

 views on the structure of the thorax, and the 

 "glossaiy and synonymy" (on pp. 570-583) 

 will prove more than ordinarily useful to sub- 

 sequent students of this subject. Many will 

 agree heartily with the protest against the 

 tendency to explain all structural differentia- 

 tion of a segment by the supposition of a mul- 



tiple origin. It is pointed out that if seg- 

 ments have been lost they have been sup- 

 pressed and not fused and are not represented 

 by the present subdivisions of the segments. 



There may be less assent to the idea of sepa- 

 rating the labial segment from the head, there 

 would be more reason for considering the pro- 

 thorax as not forming part of the thorax. 

 Much is added to our knowledge of the detail 

 of the sternal and pleural structures, but noth- 

 ing added to the interpretation of their sig- 

 nificance beyond the accumulation of evidence 

 against their supposed double origin and in 

 favor of the single origin urged by myself 

 several years ago' and the elevation of the 

 occasionally partially chitinized articular 

 membrane to the position of a component part 

 of the segment under the names of the pre- 

 sternum and preepisternum. 



In reference to the notum we find the most 

 radical views. This region is conceived of as 

 consisting of two parts, one the original chit- 

 inized portion of the segment, the other a new 

 sclerite resulting from the chitinization of the 

 articular membrane. This last portion is iden- 

 tified as the postscutellum of Audouin, tlie 

 division between other three regions of the 

 notum are supposed to be of relatively recent 

 origin and not to be homologous through the 

 group, since they do not correspond with a 

 system of internal ridges which are considered 

 as comparable in all insects. 



It is probable that in some groups many 

 authors have made mistakes in properly 

 homologizing the various parts of the dorsum, 

 but there has not yet been offered enough evi- 

 dence to cause us to overturn at once the older 

 nomenclature. 



The scutum is the piece bearing the wing 

 processes. Exactly what its anterior border is 

 may be a question for discussion. Posteriorly 

 it is probably bounded by the " V-shaped 

 ridge," but here again we may have an un- 

 settled question. The piece behind the scutum 

 is the scutellum. There is no difficulty in 

 most cases in recognizing it, but its exact 

 boundary may again be an unanswered ques- 



' " The Wing Veins of Insects," Univ. of Calif. 

 Publications, Entomology, Vol. I. 



