158 A renicolidae 



neuropodia are short, septal pouches are absent, and there are several 

 pairs of oesophageal caeca. Of the caudate species, A. marina and 

 A. assimilis present fewest modifications and stand near the bases of 

 origin of the two series. Nearly related to A. marina is A. (jlacialis, 

 their close affinity being indicated by the similarity of their 

 neuropodia, chaetae, oesophageal glands, septal pouches, nephridia and 

 statoliths; the gills and prostomium of A. glacialis also more nearly 

 resemble those of A. marina than of any other species. The chief- 

 difference between these two species is that in A. glacialis the 

 chaetiferous segments and gills are reduced in number. 



The two species A. loveni and A. cristata have apparently sprung 

 from the same stem, for in both the neuropodia are long, the gills 

 highly pinnate, the septal pouches large, and the statocysts closed and 



cristata pusilla 



branchialis 



marina assimilis 



BrancMomaldane 



each containing only a single large statolith. Further indication of 

 their affinity is afforded by the similar form of their prostomia ; 

 while, in the character of its chaetae, A. loveni presents a closer 

 approach to A. cristata than to any other species. A. loveni exhibits 

 considerable specialisation in its extraordinary septal pouches and its 

 notopodial chaetae, while A. cristata has undergone modification in 

 another direction, namely, reduction in the number of its chaetiferous 

 segments and gills. The two species A. loveni and A. cristata are 

 clearly more nearly related to each other than either is to A. marina. 

 A. assimilis and A.pusilla diverge from the rest of the species in 

 several striking features (p. 157) and have developed along an 

 independent line. A. assimilis has primitive statocysts, and its 

 prostomium is little modified, being not much dissimilar to that of 



