2l6 NATURAL SCIENCE. March, 



also with the tawny animals of the desert. Nerves are formed 

 because nervous molecular impulses seek the channels of least 

 resistance : and by repeated passing through the same channels, 

 cause a differentiation of the tissue. Cave animals are blind because 

 the eyes of many generations "have never been stimulated to their 

 full growth by light." 



Psychology contributes to the theory, the laws of Association and 

 Repetition. Professor Orr believes that the nervous system is merely 

 a specialisation of the nervous activity of cell-protoplasm, and so 

 cheerfully applies to all living matter considerations drawn from 

 psychological observations on human beings. The simplicity of 

 the theory consists in this : if you assume that outward forces are the 

 " cause " of growth and development, and that molecular changes 

 corresponding to memory of growth and development are transferred 

 to the germ-cells, it is quite clear that under similar forces the germ- 

 cells will be changed in the same way : only they will be changed 

 more quickly, because they know what they are bound to do. 



P. C. M. 



Investigations on Microscopic Foams and on Protoplasm ; Experiments and 

 Observations directed towards a Solution of the Question of the Physical Con- 

 ditions of the Phenomena of Life. By O. Biitschli, Professor of Zoology in the 

 University of Heidelberg. Authorised translation by E. A. Minchin, B.A. 

 (Oxon.), Fellow of Merton College, Oxford. 8vo. London : Adam and Charles 

 Black, 1894. Price i8s. 

 Some time ago^ in an account of the original German edition of 

 Professor Butschli's work, I was able to let readers of Natural 

 Science know that an authorised translation by Mr. Minchin was in 

 preparation. This has now appeared, and the publishers, the trans- 

 lator, and Mr. Minchin are to be congratulated. Only those who 

 have had to grapple with the perplexing German of the original can 

 appreciate how lucidly and how skilfully Mr. Minchin has interpreted 

 his author. In format the book is an improvement on the stitched 

 German quarto ; the plates have lost nothing in the transference, and 

 the convenience of the reader is consulted by the relegation to smaller 

 type of some discursive controversial matter. 



It is needless to describe at length a book which biologists have 

 now no excuse for neglecting. Professor Biitschli, in the course of 

 his well-known investigations on Protozoa, came to see that there are 

 all gradations between scattered vacuoles and a completely alveolar or 

 reticular structure. He was led in this way to interpret all reticular 

 structure in protoplasm as honey-combed structure. Then, after 

 patient effort, he succeeded in manufacturing microscopic foams that, 

 under the microscope, presented the reticulate appearance of proto- 

 plasm. In this book he describes these foams minutely and compares 

 them with protoplasm as seen in many organisms. But an unexpected 

 marvel was the appearance of streaming movement and actual pro- 

 gression in his artificial foams. The discussion and physical 

 explanation of these, and the suggestions these physical explanations 

 give for the analogous processes in living material, form the most 

 startling part of Professor Butschli's contribution to science. These 

 are all matters to be worked out with microscope and materials, 

 rather than to be discussed and criticised in writing. Do not reason 

 with a doubter, using vain words, but lead him to a laboratory and 

 show him the foams streaming and moving. P. C. M. 



iNat. Science, Jan., 1893, "Artificial Protoplasm," by P. Chalmers Mitchell. 



