194 The American Geologist. March, 1894 
the west shore of Canandaigua lake, and their contact phenomena upon 
the Trenton limestone," by B. K. Emerson; and "The Devonian Section 
of Central New York along the Unadilla River," by Charles S. Prosser. 
Om en Hemipter /run Sveriges undre' Graptolitskiffer; by Johann 
Chr. Molserg (Geolog. Forening. i Stockholm Forhandlingar, vol. xiv. 
pp. 121-124). 
The author has found a bed-bug (Protocimex siluricus) in the grapto- 
lite shales of Sweden. 
The Evolution of the Brachiopoda; by Agnes Crane. 
The Brighton Herald of Dec. 16, 1893, publishes a very full abstract of 
Miss Crane's paper prepared for one of the scientific congresses of the 
recent Columbian Exhibition and re-read before the "Brighton and Sus- 
sex Natural History and Philosophical Society." It is a lucid and 
forcible presentation of the subject by a student thoroughly in touch 
with the abundant and important results achieved in this field of inves- 
tigation during the last few years ; gracious in its acknowledgments, 
and interspersed with lively and interesting reminiscence of the late 
Thomas Davidson, whose name will always bear the ( tesarea majestas 
in matters brachiopodous. The following passage from this abstract 
seems worthy of reproduction: "It was shown that synthetic or mixed 
types were by no means rare, reversionary or atavistic forms not un- 
common : that the study of individual development of larval forms of 
recent species reveals long past phases in the history of the origin of 
genera, which agree geologically with their chronogenesis or birth in 
time. The existence of numerous passage forms, intermediate in struc- 
ture between the hingeless and hinged subclasses, showed those divi- 
sions were not based on fundamental distinctions. Ordinal evolution was 
conclusively demonstrated and numerous instances were given of the 
successive 'paterine,' 'obolleloid' and iinguloid' characters of ancient 
genera. Instances of development on parallel lines were cited in the 
families Lingulidce, Rhynehonellidae and Terebratellidse. The lecturer 
paid a passing tribute to Madame Pauline Oehlert as the only other 
member of her sex who was actively interested in the study of the 
Brachiopoda." 
Causes of Magmatic Differentiation . By Helge Backstrom. (Jour- 
nal of Geology, vol. i, No. 8, pp. 773-779, Nov.,-Dec, 1893.) 
The author thinks that "Soret's principle"' cannot be applied to the 
differentiation of igneous magmas, for we do not know what is the sol- 
vent and what the thing dissolved, nor does it seem right to apply the 
laws of dilute solutions to magmas before attempting to consider them 
simply as mixtures of liquids. He gives an illustration of how two 
liquids, aniline and water, mix at different temperatures; it is found 
that the mixture separates into two layers, which contain different 
amounts of the two liquids, and the relative proportions of the liquids 
vary in the layers according to temperature, mixing more readily as the 
temperature increases, and finally, when sufficiently heated, mixing in 
all proportions. The different parts of a rock magma may perhaps act 
