Arenicola branchialis 141 



In 1868 Claparede defined Arenicola fjrubii in the following 

 terms "Corpus longitudine 6-7 cent., latitudine 3-4 mm., nigrum 

 obscure viridescens, segmentis anticis branchiis destitutis decein, 

 posterioribus branchiatis viginti, cauda fere nulla." There is an 

 error in this diagnosis, there being eleven, not ten, anterior abranchiate 

 chaetiferous segments ; Claparede overlooked the first, a mistake 

 easily made because the first notopodium is often absent or minute. 

 Claparede remarked on the similarity of his species to A. branchialis, 

 but noted that in the latter the first pair of gills was said to be on 

 the thirteenth or fourteenth segment. 1 He described the segmental 

 organs, of which he found five pairs, the nervous system and statocysts, 

 and noted the unilateral branching of the gills. The position of the 

 first gill, the absence of tail, and the presence of five pairs of 

 nephridia and of closed statocysts, serve to fix definitely the species 

 with which he was dealing. 



The brief and imperfect description of A. branchialis given by its 

 founders has led to much confusion. Some writers have held that 

 this species was so insufficiently described that its identity could not 

 be established definitely ; others considered it to be identical with 

 A. grubii, and a few, believing ecaudata and grubii to be synonymous, 

 have united them under the earlier name branchialis. This last view, 

 based on a consideration of the gross external features only, became 

 untenable immediately the internal organs of A. ecaudata were 

 inspected. The differences between the two ecaudate species in the 

 number of their nephridia and the nature of their gonads were first 

 commented upon by l)rs. Gamble and Ashworth (1898), and Prof. 

 Mesnil shortly afterwards drew attention to differences in the number 

 of segments and gills, and in the position of the first pair of gills. 

 Accounts of the internal and external anatomy and of the differential 

 characters of this species were given by Prof. Fauvel and by Drs. 

 Gamble and Ashworth. 



NOMENCLATURE OF THE SPECIES. The possibility that A. branchi- 

 alis and A. grubii were identical has not been overlooked, but most 

 writers since the publication of Claparede's memoir (1868) have 

 preferred to use for this species the name ynibii, because it was asso- 

 ciated with a description enabling the species to be at once identified. 



The identity of A. branchialis cannot be determined by an appeal 



1 And that " Johnston, qui parait decrire la meme espece sous le nom de 

 A. ecauda [sic], 1'indique meme au quinzieme ou seizieme." Claparede evidently 

 considered branchialis and ecaudata to be synonymous. 



