THE MORPHOLOGICAL COMPOSITION OF ANIMALS. 127 



and Annelid &quot; is difficult to reconcile with the visible con 

 trast between the two. Whatever local segmentations there 

 are in an Amphioxus appear to me quite unlike &quot; in prin 

 ciple &quot; to those which an Annelid exhibits. Could its 

 portion of gut be duly supplied with nutriment., the segment 

 of a low Annelid could carry on its vital functions independ 

 ently. In the parts of the Amphioxus we see nothing 

 approaching to this. Cut it into transverse sections and no 

 one of them contains anything like the assemblage of struc 

 tures required for living. The Amphioxus is a physiological 

 whole, and in that respect differs radically from the Annelid, 

 each segment of which is in chief measure a physiological 

 whole. No occurrence of local segmentation in the Am 

 phioxus can obliterate this fundamental contrast. 



An accompanying contrast tells the same story. On as 

 cending from the lowest to the highest annulose types we 

 see a progressing integration, morphological and physiologi 

 cal; so that whereas in a low annelid the successive parts 

 are in large measure independent in their structures and in 

 their lives, in a high arthropod, as a crab, most of the parts 

 have lost their individualities and have become merged in a 

 consolidated organism with a single life. Quite otherwise is 

 it in the vertebrate series. Its lowest member is at the very 

 outset a complete morphological and physiological whole, and 

 the formation of those serial parts which some think analo 

 gous to the serial parts of an Annelid, begins at a later stage 

 and becomes gradually pronounced. That is to say, the course 

 of transformation is reversed.] 



