Arenicola assimilis 129 



from that remote island 1 it is worthy of careful re-examination. 

 The specimen is in three pieces, which, when joined together, are 

 208 mm. in length, of which the tail forms 74 mm. Assuming that 

 all the parts are present, which is apparently the case, there are 

 nineteen chaetiferous segments, the last thirteen of which bear gills. 

 The writer is unable to confirm Grube's statement regarding the 

 composition of the branchial segments, for, in each of the segments 

 of this region in which the annuli are distinguishable, there are five, 

 although one of them may be rather smaller than the others. The 

 neuropodia are of the short type found in A. assimilis and pusilla. 

 The outline of the prostoniial lobes is sufficiently retained to show 

 that the prostomium agrees with that of A. assimilis. Oesophageal 

 glands are wanting, owing to damage, probably at the time of 

 capture. Septal pouches were found to be absent. The number of 

 nephridia cannot be ascertained on account of the damaged condition 

 of the anterior nephridial region, and the search for statocysts was 

 precluded by the leathery condition of the anterior end. The 

 diagnosis rests, therefore, almost entirely on the form of the 

 prostomium and the crotchets (Fig. 22s, p. 51), but the writer has 

 no hesitation in referring the specimen to the species A. assimilis 

 var. affinis. 



Prof, von Marenzeller recorded Arenicola marina from Angra 

 Pequeria (Liideritzbucht), but examination (Ash worth, 1911) of 

 extensive well-preserved material from that bay, and of one of Prof, 

 von Marenzeller's original specimens, 2 showed that the species which 

 occurs there is A. assimilis var. affinis. Ives' statement that A. marina 

 occurs in South Africa is based upon Prof, von Marenzeller's work. 



1 Since this account was finished M. Ch. Gravier has published notes on an 

 example of Arenicola from Kerguelen (Bull. Mus. Hist. Nat. Paris, xvi (1910), 

 p. 198; Ann. Inst. Oceanogr., iii, fasc. 3 (1911), p. 35). The specimen was 

 incomplete and in a very bad state of preservation. M. Gravier has referred it, 

 but under great reserve, to A. assimilis. Prof. Ehlers has kindly informed me 

 that among the collection made at Kerguelen by the German South Polar 

 Expedition there is a specimen of A. assimilis var. affinis. Had M. Gravier's 

 specimen been complete it would probably also have been found to belong to 

 the variety affinis. 



2 This specimen was not in good condition at the anterior end, the outlines 

 of the prostomial lobes were defectively preserved, statocysts could not be demon- 

 strated, and only five pairs of nephridia were present, so it was recorded 

 (Mitt. Zool. Mus. Berlin, iv (1910), p. 351) as A. claparedii. Subsequent 

 microscopic examination of the stained and cleared anterior end showed that 

 there were remains of a statocyst on one side (the rest of this organ and that of 

 the other side had disappeared owing to maceration), and therefore the former 

 determination was incorrect. The specimen is A. assimilis var. affinis, and 

 agrees with all other South African examples of this species in having only five 

 pairs of nephridia. 



K 



