1878. ] Recent Literature. © 243 
Cephalothrix, Drepanophorus) that they pass through three prin- 
Cipal stages. : 
I. A bilateral Gastrula-form. 
II. A Gastrula, with the middle layer (mesoderm) arising from 
the exoderm, and composed of two principal rudiments: (1) the 
muscular layer, thin and uniform; (2) the recticulum, extending 
through the entire body-cavity, and represented in the embryos 
of Lineus obscurus by oil globules. 
III. The longitudinal layer is enlarged in advance of the lateral 
organs into a solid mass; the nervous system arises over all the 
internal extent of the layer thus complicated. The internal cavity 
is divided, into a system of cavities separated by partitions, all 
along which the reticulum is applied in a continuous layer. 
These three states, which may be successively observed in the 
embryo of a nemertean worm, appear to exist in a more explicit 
way in Prorhynchus, where state II seems to be represented by 
an adult, free-living Planarian. The Nemerteans, then, appear to 
have derived from a sudden modification of the Planarian type, 
and justify, in the author’s opinion, the establishment of homol- 
ogies between the two groups. 
Tuomas’ Noxious Insects oF ILitno1s!'—This interesting re- 
port is divided into two parts, the first relating to horticultural 
entomology, and the second comprising the introductions to and 
first part of a manual of economic entomology for the State of 
Illinois, including the Coleoptera. The first part contains excel- 
lent advice concerning the best means of contending against in- 
sects injurious to the orchard, especially general and preventive 
remedies, which are always the best and usually the last to be ap- 
plied. Considerable attention is bestowed on the birds found to 
be useful in the orchard, and a list is given of the most important 
species. The report will prove very useful and timely to the 
farmers and gardeners of Illinois, for whose sole use it has been 
compiled. 
CONTRIBUTIONS TO THE FossiL FLORA OF THE WESTERN TERRI- 
TORIES. Part II, Tue Tertiary FLora. By L. Lesquereux.2— 
In this important work Prof. Lesquereux gives to the world the 
results of many years of laborious investigation of the remains 
of plants which have been discovered in the later horizons of the 
ocky Mountain region from the Laramie formation upwards, by 
the U.S. Geological Survey under Dr. Hayden, and by Messrs. 
Berthoud, Le Conte, Denton and Allen, Profs. Lakes and Cope, 
Lieut. Vogdes and others. After considering the stratigraphy of 
1 Sixth Report of the State Entomologist on the noxious and beneficial Insects of 
the State of Iilinois. The first biennial Report. By Cyrus THOMAS, PH.D., St 
Entomologist. Springfield, Ill., 18 7, 8°, pp. 174, iv, ii. 
2 Report of the United States Geological Survey of the Territories. F. V. HAYDEN, 
U.S. Geologist-in-charge. Vol. vii. 4to, pp. 360. 1878. 
