TIIE MORPHOLOGICAL COMPOSITION OF AXIMALS. 



91 



it, we find a variety of types having the looked- for charac- 

 ters. Let us contemplate some of them. 



§ 205. An adult Annelid is composed of segments which 

 repeat one another in their details as well as in their general 

 shapes. Dissecting one of the lower orders, such as is 

 160, proves that the successive segments, be- 



shown in Fig 



ivies having like locomotive appendages, like branchiae, and 

 sometimes even like pairs of eyes, also have like internal 

 organs. Each has its enlargement of the alimentary canal ; 

 each its contractile dilatation of the great blood-vessel ; each 

 its portion of the double nervous cord, with ganglia when 

 these exist ; each its branches from the nervous and vascular 

 trunks answering to those of its neighbours ; each its simi- 

 larly answering set of muscles ; each its pair of openings 

 through the body- wall ; and so on throughout, even to the 

 organs of reproduction. That is to say, every segment is in 

 great measure a physiological whole — every segment con- 

 tains most of the organs essential to individual life and mul- 

 tiplication : such essential organs as it does not contain, 

 being those which its position as one in the midst of a chain, 

 prevents it from having or needing. ' If we 



ask what is the meaning of these homologies, no adequate 

 answer is supplied by any current h}^othesis. That this 

 " vegetative repetition " is carried out to fulfil a prede- 

 termined plan, was shown to be quite an untenable notion 

 (§§ 133, 134). On the one hand, we found nothing satis- 

 factory in the conception of a Creator who prescribed to him- 



