THE PRIMEVAL AMERICAN CONTINENT. 229 



which pass througli an essentially similar develojDment, there is no 

 stalk ; and the animal, after its free-swimming stage, simply glues its 

 head, by a kind of marine cement of its own manufacture, to the rock, 

 develops its conical shell, and like the barnacle uses its modified feet 

 as means for exercising the commissariat and nutritive function. It is 

 true that in some respects the adult barnacle may be regarded as lower 

 than the young, and therefore as a degenerate being. Thus, it is 

 lower when eyes, feelers, and movements are taken into account. In 

 other respects the adult may be considered of higher organization than 

 the larva. These higher traits we may logically enough supj^ose rep- 

 resent the special advances which adult barnacle-life has made on its 

 own account. But, on the w^hole, degradation and retrogression, if not so 

 fully exemplified as in the sacculina, is still plainly enough illustrated 

 in barnacle historv. When we further reflect that even such hisch 

 crustaceans as prawns and allied forms begin life each as a " nauplius " 

 or under an allied guise, we not only merely discover the common 

 origin of all crustaceans in some form represented by the " nauplius " 

 of to-day, but we also witness the possibilities of development which 

 have placed shrimps, prawns, etc., in the foremost rank of the class, and 

 which, conversely, have left the barnacles and sacculinas, through the 

 action of degenerative changes, among the groundlings of the grouj). 



The assumption of a sedentary life, whether parasitic in nature 

 like that of sacculina, or whether it is represented by mere attachment 

 and fixation to some inorganic thing, as in the case of the barnacles, is 

 therefore seen to operate in the direction of producing degeneration 

 of the animal's constitution. The tendency of such habit is toward 

 simplification of structure and not toward that progressive advance 

 and evolution which, in the case of the higher crustacean races, have 

 evolved from the relatively simple " nauplius " of the past the crabs, 

 lobsters, shrimps, and prawns of to-day. Gentleman^ s Magazine, 



[To he continued. '\ 







T 



THE PKBIEYAL AMEKICAIS' COXTmENT. 



By L. p. GEATACAP, A. M. 



HE reader may recall standing, when a child, by the side of a 

 -L toy-dam in the course of some little stream, and, were a breach 

 made in the mimic masonry, remember the mute interest with which 

 he watched the slow emergence of fairy islands as points of rock and 

 shoals of mud slowly appeared above the water's surface how the 

 detached summits, at first round spots, assumed varied outlines in- 

 dented with cones or bristling with promontories; how they multi- 

 plied as the ebbing water exposed newer and lower levels, until the 



