April 1-2, 1895.] 



SCIENCE. 



413 



climatic changes of the glacial period 

 resulted from the combined influence of 

 precession of the equinoxes and sec- 

 ular changes in the eccentricity of the 

 earth's orbit. In favor of this view, the 

 mean temperature of the globe was lowered, 

 and the ratio of the precipitation increased ; 

 the dominant set of the currents in the At- 

 lantic was from north to south in the colder 

 terms. In the interglacial climates the 

 summers were cooler and the winters 

 warmer, while the Atlantic cui-rents flowed 

 northerly. The maximum glaciation came 

 early, succeeded by cold epochs of diminish- 

 ing severity. Glacial epochs in the north- 

 ern hemisphere were necessarily contempo- 

 raneous with interglacial conditions in the 

 southern hemisphere. Hence the astronom- 

 ical theory would appear to ofier the best 

 solution of the glacial puzzle ; while it is 

 conceded that this answer is not completely 

 satisfactory. C. H. Hitchcock. 



Biological Lectures and Addresses, by Ak- 



THCR MiLXEs Marshall. Macmillan & 



Co., New York. Price S2.25. 

 Lectures on the Dartcinian Theory, by Arthur 



MiLXEs Marshall. Macmillan & Co., New 



York. Price S2.25. 



It was a curious coincidence by which ac- 

 cidents in mountain climbing deprived Eng- 

 lish science of two of its prominent biolo- 

 gists, and two who were at the same time 

 personal friends. Prof. F. M. Balfour, as 

 every one remembers, lost his life in a 

 journey in the Alps, and Prof. Arthur Milnes 

 Marshall, upon the last day of 1893, in a 

 somewhat similar manner, met his death in 

 mountain climbing. Prof. Balfour and 

 Prof. JIarshall were personal friends and 

 naturally worked upon kindred subjects, al- 

 though their work was very unlike. Prof. 

 Marshall was still a young man, only about 

 forty years of age. Early in life he entered 

 upon studies looking toward the profession 

 of medicine, but in 1879 gladly accepted the 



chair of Zoology in Owens College, and con- 

 tinued to occupy the chair until his death. 



His additions to the literature of science 

 have been of two general types. There are 

 first a series of papers embodj'ing the results 

 of oi-iginal research. These, because of his 

 intimate association with Balfour, were at 

 fii-st of an embryological nature, while some 

 of the later ones were more distinctly ana- 

 tomical. His chief contributions to science 

 of this sort were upon the Serjmental value of 

 Cranial Xerves, the Pennatulida of the Por- 

 cupine a7id Triton E.rpeditions, and upon The 

 Nervous System of the Crinoids. The second 

 class of his papers were more distinctly 

 characteristic of his special powers. They 

 were of a more general character and in- 

 cluded a text-book on The Frog, on Practical 

 Zoology, and a more recent work upon T er- 

 tebrate Embryology. In addition, we have 

 in the recent posthumous volumes a large 

 number of lectures and addresses given in 

 various places before various societies. 



Above all things, Professor Jlarshall was 

 a teacher. It was in this direction that his 

 powers showed at their best. He had the 

 happy way of putting subjects so that they 

 were intelligible to his audiences, and had the 

 somewhat unusual power of putting himself 

 in the position of his audiences, in such a 

 way that he could understand how and 

 what was needed in his teaching to render 

 his subjects clear. His lectures were always 

 abundantly illustrated both by drawings, 

 and especially by homely though terse illus- 

 trations. His illustrations for rendering 

 scientific fiicts intelligible were drawn some- 

 times from the most surprising sources, and 

 altogether rendered his addresses and his 

 class lectures of the very highest character 

 in the way of scientific teaching. Since his 

 death Macmillan & Co. have published his 

 collected lectures and addresses in the two 

 volmnes which are the subject of this notice. 

 The first series consi.sts of miscellaneous 

 addresses given by him at various intervals 



