276 THE RELATIONS OF SPECIES 



parasitic Distomas, Tetrastomas, Octobothriums, &c. On the 

 whole, it would seem that this strange anomaly contains many 

 more of the worm-like features than of others, and if we add, to 

 the last-mentioned group of characters, the short feet, (cl,) with 

 their protrusile bristles, we may assume that we have before us 

 a peculiar kind of worm, combining in itself the organization of 

 the Intestinal worms and the true Annulata, or Aquatic worms, 

 and therefore standing as an intermediate form, or group, be- 

 tween the former and the latter. 



Such are, in brief, the links which unite these apparent anom- 

 alies of nature. Several of them have occupied the attention of 

 zoologists for many years ; and notwithstanding their anatom- 

 ical characters have been reviewed again and again, their defi- 

 nite position among the various groups of Articulata remains 

 undetermined to the present day. Those who are satisfied that 

 animals are related to each other through inosculating, or inter- 

 locked groups are content with their present understanding of 

 the general relations of these forms ; but that class of natu- 

 ralists who think they see in every kind of animal a distinct, 

 circumscribed idea, will always be straining their nerves to the 

 utmost to fit every stray piece to its exact mate in the gigantic 

 puzzle. 



As we rise from the consideration of general relations to the 

 more specified and circumscribed, i. e., from those which run 

 through the whole animal kingdom to those which more espe- 

 cially characterize the great groups or divisions, and from these 

 pass on to the characteristics of the classes, (or subdivisions 

 of the great groups,) we find the features of the minor groups 

 have more of the nature of what are commonly called family 

 traits, or such as would be usually recognized as the physiog- 

 nomy of near blood-relationship. 



But now we have, as it were, only just begun to get an in- 

 sight of the still closer and more numerous affinities which are 

 common to the various species of animals. Among the Song- 

 sparrows, for instance, who can say how many characters they 

 have in common ? Beside the more general characters which 



