224 SOME NEW BOOKS [SEPTEMBER 
by Dr. Sharp last year at Cambridge before the International Zoological 
Congress. Here he restricts himself to a record of the facts of insect life and 
structure, and perhaps by the absence of any trace of a phylogenetic tree he 
silently rebukes the rashness of younger men. Gro. H. CARPENTER. 
DR. WILLEY’S RESULTS. 
Zoological Results based on Material from New Britain, New Guinea, 
Loyalty Islands, and elsewhere. Collected during the years 1895, 
1896, and 1897. By ArtTHUR WILLEY, D.Sc. (Lond.), Hon. M.A. 
(Cantab.) Part III. pp. 207-356, pls. xxiv.-xxxiil. Cambridge Uni- 
versity Press, 1899. Price 12s. 6d. 
Part III. of Dr. Willey’s ‘Zoological Results” contains articles by Dr. 
Gadow, Mr. Shipley, and the author. Dr. Gadow gives an interesting account 
of the variations to be found in the carapace of young chelonians. We 
must assume that the course of evolution in the chelonian branch of reptiles has 
been in the direction of a steady reduction in the number of scutes covering the 
carapace, in accordance with a “widespread evolutionary law” of the “specialised 
few” replacing the ‘ generalised many.” 
The turtlets show a greater percentage of abnormalities in the carapace than 
the older individuals. ‘Our Turtlets start with many, with at least 24 dorsal 
scutes (leaving out the marginals), and then reduce them to 16. In other 
genera the reduction has advanced to 14, to 13, and individually to 12. This 
means onward development. The ideal, the goal for the young Caretta, is the 
possession of a 16-scuted shell. Those which start with 24 perhaps never reach 
’ the ideal, but this failure does not seem to hurt them, natural selection remains 
indifferent. Others start with 22, 21, 20, 19, or 18 scutes, and the latter 
individuals are rather common in the newly-hatched stage, and all of these seem 
to reach the goal. . . . These variations from the normal type all lie in the 
direct line of descent, and the more serious the variation the farther back it 
points. Moreover, the changes necessary to turn any given variation into 
another one less abnormal, until ultimately the normal condition is reached, are 
not erratic, but stand in strict correlation with each other, and proceed strictly 
on definite lines. I therefore call this kind of atavistic variation orthogenetic.” 
This orthogenetic variation in young chelonians appears to be a very striking 
example of Van Baer’s law in its modern application. 
Dr. Willey follows with a valuable contribution to our knowledge of the 
Enteropneusta. Firstly, he gives a synopsis of the groups under the three 
families of Ptychoderidae, Spengelidae, and Balanoglossidae, followed by a detailed 
description of Ptychodera flava, P. carnosa n. sp., P. ruficollis n. sp., with 
Spengelia porosa, Willey, and S. alba n.sp., with notes upon the West Indian 
species Pt. biminiensis n.sp., and Pt. jamaicensis n. sp. 
There are many interesting points upon which one could dwell in these 
descriptions, but space will not permit. Spengelia appears to offer some 
remarkable features, including the so-called vermiform process of the stomochord 
(the latter is a useful name suggested by the author for the “notochord” of 
the Enteropneusta), and the presence of truncal canals. Dr. Willey finishes his 
paper by a discussion of the ‘“‘ Morphology of the Enteropneusta.” He pro- 
pounds a theory of the origin of gill-slits, based principally on their relation- 
ship to the gonads in this group. 
Gill-slits primarily arose as inter-zonal depressions between the zonary, 
metamerically repeated gonads, functioning for the oxygenation of the gonads. 
Later they acquired openings into the pharyngeal wall, and were used for the 
respiration of the individual. 
Further, he comes to important conclusions with regard to the stomochord of 
Enteropneusta and related organs in Cephalodiscus and Actinotrocha, which 
