IM ZOOLOGY. 



divided. At first, for example, its dentition is the type of Un- 

 common trout; as it grows it assumes the character which 

 we find to prevail in some of the Forelle or sea trout. La>tly, 

 it assumes the true salmon dentition ; but that which espe- 

 cially merits attention is, that the original type of the generic 

 being is of a character so ample as to embrace all possible 

 forms which the dentition can assume in any species of that 

 natural family. Nothing is wanting; nothing new appears : 

 nothing has to be supplied; all is foreseen; all provided for. 

 To institute a species, all that is required is to omit, or cause 

 to disappear, or cease to grow, some parts of the organ or 

 apparatus already existing in the generic being. In every 



Fig. 421. Palemon* (Pakemon, Fab.). 



natural family there is a species which bears, to the generic 

 animal, that is, to the young, a stronger resemblance than any 

 other. In the Salmonidse it is the common trout of fresh- 

 water rivers, but there may be others. In the solipede it 

 seems to be the quagga of Southern Africa." R. K.] 



563. The lateral appendages of the various rings con- 

 stituting the body are in general very numerous, and present 

 also considerable differences in their conformation and their 

 U86B, whether we consider them in the various parts of the 



* a, antennae of the first pair; ai, antenna? of the second pair, or inferior 

 antennae ; /, lamellated appendix covering the ' mm, <ir frontal 



prolongation of the carapace; y, eyes; pm, external limb-jaw: p', thoracic 

 limb of the first pair ; p", thoracic limb of the second pair ; fp, false swim- 

 ming limbs of the abdomen ; , caudal fin. 



