Geology and Natural History. 157 



the original almost too closely, and that a little more freedom 

 would have sometimes made the rendering smoother and more 

 readily intelligible. It would have been well too if the oppor- 

 tunity had been taken to correct occasional misstatements in the 

 original. 



6. A " Manual of American Land Shells" by W. G. Binney. 

 Bulletin No. 28 of the U. S. National Museum. — This work is an 

 enlarged and revised edition of the "Land and Fresh-water Shells 

 of North America, Part I," published by the Smithsonian Institu- 

 tion in 1869. Of its 528 pages the author devotes about fifty to 

 the subjects of "geographical distribution; organs of generation, 

 jaw and lingual dentition, and classification, 425 to the descrip- 

 tion of genera and species, and twenty-eight to a detailed cata- 

 logue of the Binney collection of land shells of North America, 

 which Mr. Binney presented to the National Museum. The vol- 

 ume includes only the Geophila among the Pulmonata. The 

 author accepts the division into families in Dr. Paul Fischer's 

 recent work, but follows Alber's "Du Helicum," by Von Martens, 

 in the Genera. The arrangement is not systematic, but accord- 

 ing to geographical distribution. It is strange that at this day 

 the author should have to regret the lack of data for determin- 

 ing satisfactorily this distribution. Thirteen species are stated to 

 be universally distributed over the United States. Eleven foreign 

 species occur on the sea-coast. Limax maximus is reported only 

 from Newport, R. I., New York city and Philadelphia. We have 

 found it abundantly in gardens in New Haven, Conn. a. g. d. 



7. Ptasmolytic Studies. — In 1884, Professor Hugo de Vries of 

 Amsterdam published an account of a new method for determining 

 the osmotic capacity of cells. It ic well known that in dilute 

 solutions of neutral salts the protoplasm of active healthy cells is 

 little affected until after the lapse of considerable time, but that 

 in stronger solutions of the same salts there is an immediate 

 contraction of the protoplasmic contents, together with a separa- 

 tion of the mass from the walls at all points except where delicate 

 threads still maintain their hold. By a long series of experiments, 

 de Vries determined the strength of various salts by which this 

 contractile action could be produced, and he ascertained also the 

 effect in different cases upon the turgescence of the cell-wall itself. 

 The same investigator has continued his observations and extended 

 them into a contiguous field, namely, the behavior of the so-called 

 vacuoles, or sap cavities of protoplasm, under the influence of the 

 various contracting or plasmolytic agents. Reserving for a later 

 issue an extended account of the whole paper, it may now be 

 mentioned that he has discovered an interesting fact, susceptible 

 of easy verification, that a minute trace of ammonia causes in 

 every case a remarkable increase in the size of the vacuoles and 

 completely changes their capacity for absorption. The bearing 

 of this fact upon the curious observation of Darwin on the 

 phenomena of " aggregation " appeared worthy of immediate 

 attention. Hastily conducted observations with reference to this, 



