7G0 J. n. AsnwoRTii. 



lY. Systcmntic Position of Aronicola assimilis and of 

 tlio Specimens from New Zealand. 



Arenicola assimilis is clearly distinguished from all 

 other species by the following characters: — (a) externnlly, by 

 its twenty clifictigerons segments and the presence of the 

 first gill on the eighth segment; and {h) internally, by the 

 possession of six pairs of nepliridia opening on the fourth to 

 the ninth segments, 1)3^ the presence of numerous oesoplingeal 

 glands and of large otocysts opening to the exterior, and by 

 the absence of the pouches on the first diaphragm. 



This species obviously falls within the caudate section of 

 the genns Arenicola. It has practically no points in com- 

 mon with A. cristata except those of generic valne ; the two 

 species differ in every one of the characters named above. 

 Ehlers' species has some points of resemblance to A. 

 claparedii ; in fact, the two most characteristic features of 

 the latter species are fonnd in A. assimilis, viz. the 

 multiple oesophageal glands and the absence of dia])hrag- 

 matic pouches. But these two species are clearly distin- 

 guished by the differences in the number of segments, the 

 position of the first gill, the number of nephi'idia, and the 

 presence in A. assimilis of large otocysts, such organs being 

 absent in A. claparedii. 



The structures hitherto believed to be diagnostic of 

 A. marina are also fonnd in Ehlers' species, viz. six pairs 

 of nephridia opening on segments 4 to 9, and a pair of 

 opon otocysts. 'JMiese two species maybe easily differentiated 

 by an inspection of the number of segments, the position of 

 the first gill, the oesophageal glands, and the first diajdiragui 

 (to ascertain the presence or absence of ]iouches). 



So that, although related in some degree to A. marina 

 and A. cla])ai'edii, A. assimilis is quite distinct from 

 either, and may be easily determined by i-eference to the six 

 charactei-s given above. 



The determination of the systematic position of the New 



