March 30, 1900.] 



SCIENCE, 



503 



selection may be crowded into the early 

 stages of ontogeny by post selection. Evi- 

 dently the degenerate condition is not 

 crowded back for the same reason. How 

 it is crowded back I am unable to saj'. A 

 satisfactory explanation of this will also be 

 a satisfactory explanation of the process by 

 which individually acquired characteristics 

 are enabled to appear in the next genera- 

 tion. The facts, which are patent, have 

 been formulated by Hyatt in his law of 

 tachygenesis. 



Cessation of development takes place 

 only in so far as the number of cells are 

 concerned. The number of cell generations 

 produced, being continually smaller, result 

 in an organ as a consequence also smaller. 

 In this sense we have a cessation of devel- 

 opment (cell division, not morphogenic 

 development) in ever earlier stages. That 

 there is an actual retardation of develop- 

 ment is evident from Amblyopsis and Typh- 

 lichthys in which the eye has not reached 

 its final form when the fish are 25 mm. 

 long. 



Histogenic development is a prolonged 

 process and ontogenic degeneration is still 

 operative at least in Amblyopsis. 



Degeneration in the individual is not the 

 result of the ingrowth uf connective tissue 

 cells as far as I can determine. It is rather 

 a process of starving, or shriveling and 

 resorption of parts. 



From the foregoing it is evident that 

 ■degeneration has not proceeded in the re- 

 verse order of development, rather the 

 older normal stages of ontogenic develop- 

 ment have been modified into the moi'e 

 recent phyletic stages through which the 

 eye has passed. The adult degenerate eye 

 is not an arrested ontogenic stage of de- 

 velopment but a new adaptation and there 

 is an attempt in ontogeny to reach the de- 

 generate adult condition in the most direct 

 way possible. 



Carl H. Eigenmann. 



SCIENTIFIC BOOKS. 

 The Ore Deposits of the United States and Canada. 

 By James Furman Kemp. Third Editioa en- 

 tirely rewritten and enlarged. New York 

 and London, The Scieutilic Publishing Com- 

 pany. 1900. 



The first edition of ' Kemp's Ore Deposits of 

 the United States' appeared in 1893. The 

 second edition from the same plates, in which 

 forty to tifty pages of additional matter had 

 been inserted, was published in 1895. We now 

 have the third edition, with entirely new plates, 

 which forms a volume nearly twice as thick as 

 the first, with larger type, heavier paper and 

 additional plates which contribute, as well as 

 the new matter, to its increased size. As this 

 is practically the only modern work dealing in 

 any adequate fashion with this important sub- 

 ject, and as it hence constitutes the standard 

 work for reference with regard to the ore de- 

 posits of tlie United States and Canada, it is 

 important to consider its shortcomings as well 

 as its merits, and even to dwell upon the for- 

 mer. 



It must be evident to all who consult the 

 work that Professor Kemp has been remarkably 

 thorough in his search of the literature of his 

 subject and few books have a more complete 

 bibliography ; the references, moreover, are 

 distributed throughout the text, not lumped 

 together at the end, so that it requires very lit- 

 tle labor on the part of the reader to go back to 

 original authorities on any given point. Kemp 

 possesses, moreover, in a high degree the im- 

 portant faculty of reading intelligently and of 

 expressing concisely the leading facts gathered 

 in the course of his reading. This is perhaps 

 the most important qualification for a work that 

 is essentially a compilation rather than an orig- 

 inal treatise. 



For a philosophical treatment of phenomena 

 like ore deposits, in which diflferent observers 

 may in all honesty draw diametrically different 

 conclusions from their respective examinations 

 of the same deposit, it is essential that the 

 author should have been able by personal in- 

 spection to verify the relative accuracy or de- 

 gree of probability of opposing views ; for in 

 this case, even if we may differ with the author's 

 theoretical opinions, we know that the coeffi- 



