THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES. ] 



Art. I. — The Origin and Significance of Spines : A Study 

 in Evolution; by Charles Emerson JBeecher. (With 

 Plate I.) 



Introduction. 



The presence of spines in various plants and animals is, at 

 times, most obvious to all mankind, and not unnaturally they 

 have come to be regarded almost wholly in the light of defen- 

 sive and offensive weapons. Their origin, too, is commonly 

 explained as due to the influence of natural selection, resulting 

 in the greater protection enjoyed by spiniferous organisms. 

 But when, upon critical examination, it is seen that some ani- 

 mals are provided with spines which apparently interfere with 

 the preservation of the individual, that other animals develop 

 spines which cannot serve any purpose for protection or other- 

 wise, and that spines themselves are often degenerate or sup- 

 pressed organs, then it becomes evident that the spinose condi- 

 tion may have other interpretations than the single one of pro- 

 tection. 



The object of this article is to make a few observations on 

 spinosity, especially among invertebrate animals, and to 

 endeavor to arrive at some general conclusions relating to the 

 origin and significance of this condition. It is believed that 

 the results have a broader application than is at first apparent, 

 and underlie important laws and principles of organic evolu- 

 tion. In closely related species, the presence or absence of 

 spines seems in itself a trivial character, indicating at best only 

 specific differences, yet it will be shown that the spines are 

 often the expression of important vital adjustments and condi- 

 tions, and are not merely external features of the same value 



Am. Jour. Sci. — Fourth Series, Vol. VI, No. 31. — July, 1898. 



1 



