1880. ] Recent Literature. 667 
of “ the abdominal appendages, which, in Machilis, are movably 
articulated to the hinder margin of the sterna of the eight ante- 
penultimate somites, a pair to each somite.” These as well as 
similar ones in Scolopendrella, he compares to the exopodite of 
Decapod Crustacea, notably Peneus, and thinks this an additional 
argument for the crustacean origin of insects. Now while Mr. 
Mason has pointed out some interesting points of resemblance 
between the Crustacea and insects, we do not think that these 
crustacean features have been derived from the Crustacea; but 
that they have independently arisen in the ancestral forms of each 
class. It will be interesting to follow up Mr. Mason’s “ suspicion 
that the limbs of myriopods are not strictly homologous with 
` those of insects, but that they correspond with the rudimentary 
appendages of Machilis, and are consequently exopodites, the ap- 
pendages of the legs in Scolopendrella representing the legs of 
insects, which would appear to be endopodites.” This may or 
may not be the case, but we should not desire to fall into the 
error of drawing too close homologies between two sub-ciasses 
like the hexapodous and myriopodous Tracheata (insects). 
Finally, our author, after considering the remarkable difference 
in the position of the genital openings exhibited by the different 
groups, and. very generally by the opposite sexes of Arthropoda, 
believes this is “ intelligible on the hypothesis that all the members 
of the sub-kingdom have descended from some worm-like crea- 
ture, provided in every somite of its body with a pair of seg- 
mentai organs or nephridia, and that different pairs of these organs 
have, in different descendants of this hypothetical ancestor, been 
connected in the genital aperture and ducts.” 
n a paper on the affinity of the genus Polyctenes, Mr. C. O. 
Waterhouse conclusively proves, by a winged form closely allied 
to the wingless Polyctenes, that this insect belongs near the Hip- 
poboscidz, or horse-ticks and bird-flies. In a brief paper on the 
natural affinities of the Lepidoptera hitherto referred to the genus 
Acronycta, M. A. G. Butler removes several of the species 
to the Arctiidae, a subdivision of Bombycid moths. Our own ob- 
servations on the structure of the head as well as the general form 
of the body, made several years ago, lead us to think that such a 
removal is quite unwarranted, and that the interesting analogies 
to the Bombycids are superficial, and not fundamental. 
` __ Recent Books AND PAMPHLETS.—Descripiion of four new species of Silurian 
Fossils. By S. A. Miller. (From Jour. Cin, Soc. Nat. Hist, July, 1880.) 8vo, 
PP- 5, Pl. 1, 1880. From the author. 
_ The Three Climates of Geology. By C. B. Warring. (From Penn Monthly, 
June, 1880.) 8vo, pp. 36. From the author. 
Contributions to Invertebrate Paleontology, Nos. 2-8. By Dr. C. A. White. 
(Ext. from the Tweflth Annual Report-of U. S. Geolog. Surv., 1878.) 8vo, pp. 
171, Pls. 42. From the author 
The Hessian Fly. By Ñ. S. Packard. (Bull, No. 4, U.S. Ent. Com.) Svo, 
PP. 43, Pls. 2, Map r. From the author. 
