THE MORPHOLOGICAL COMPOSITION OF ANIMALS. 99 



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 hypothesis. 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- 

 self a certain unit of composition for all creatures of a par- 

 ticular class, and then displayed his ingenuity in building up 

 a great variety of forms without departing from the " arche- 

 typal idea." On the other hand, examination made it mani- 

 fest that even were such a conception worthy of being enter- 

 tained, it would have to be relinquished; since in each class 

 there are numerous deviations from the supposed " archetypal 

 idea." Still less can these traits of structure be accounted 



