CRUSTACEA. 25 



frightened by a loud noise, such as thunder, or the firing 

 of a cannon. Such anecdotes in science-teaching are 

 simply useful as a relief from what ought to be close 

 application to the direct observation of the thing which 

 is being taught. All things are curious to the child, 

 presenting themselves as problems in need of explana- 

 tion, and he will seek nature for the sake of these 

 explanations, if we do not lead him to think of it as a 

 storehouse of curiosities and mysteries kept on hand 

 for his amusement, in place of what it is, — an original 

 source of knowledge. 



Not only is there a difference in the size of these 

 appendages, but it sometimes happens they are much 

 distorted, owing, probably, to injuries received after 

 the lobster moults and before the new shell is formed. 



Faxon figures and describes a number of these deformed 

 jaws.* It is interesting to observe the strongly-marked 

 tendency possessed by these organs to reproduce facsimiles 

 of themselves. .Most of the extra growths have assumed 

 the form of jaws witli serrated inner edges, though the 

 teeth are of no use. as both jaws are immovable. 



A more remarkable proof of this inherent power is found 

 in several specimens in the museum of the Boston Society 

 of Natural History, in which additional articulated sections 

 have grown out. and true movable jaws have been formed. 



These extra growths are the results of disease occa- 

 sioned by the irritation arising from bites, cuts, etc., but 

 tiny illustrate the general law of reproduction. In nature 

 the result of extra growth, whether occasioned by such 

 causes, or by a cell dividing, or a branch or an organ 



* See article "On Some Crustacean Deformities." in Bulletin 

 of Museum of Comparative Zoology . Harvard College April 

 1881. 



