KNOWLEDGE OF AFFINITIES DERIVED FROM METAMORPHOSIS. 51 



find many points of analogy between the order Carnivora among 

 Mammals, and that of Raptores among Birds ; each including 

 those predaceous species, which are especially adapted to capture 

 and devour the weaker kinds ; and each having its own particu- 

 lar type or plan of structure adapted to this purpose, in a manner 

 that strongly reminds us of the other. It is by the existence of 

 these analogies among distant groups, that the Unity of the Plan 

 of the Animal Creation is most clearly manifested ; and every 

 one which we discover affords us a new, and often very striking, 

 glimpse of this design. The most important of them will be 

 pointed out in their proper places. 



32. Further, the changes of form which many tribes of ani- 

 mals undergo, and of which we as yet have but a 

 very imperfect knowledge, are often very im- 

 portant in classification ; as indicating relations 

 which we should not have otherwise suspected, 

 between different groups. Thus, there is a cer- 

 tain parasitic animal of very strange form, whicli 

 attaches itself to Fishes, and is 

 named Lerncca (Fig. 7) ; the 

 true position of which in the 

 animal scale was not known, un- 

 til it was ascertained that it passes 

 through a larva, or imperfect 

 state (Fig. 8), in which it bears Fio 8 _ LARVA OF 

 so very close a resemblance to the 

 larva (Fig. 9) of the Cyclops 



Fio. 7 LERNJEA, 



THE LERNVEA. 



Fio. 9. LARVA OF THE CYCLOPS. 



Fio. 10. CYCLOPS, 



(Fig. 10), a little animal common in pools, and known under 



2 



