ARENICOLID^E ECAITDATA. 71 



from Heligoland. The same year l he wrote an important paper on the " auditory " 

 organs of Arenicola marina, A. Claparedii, A. Grubei, A. antillensls, and reviewed the 

 occurrence of homologous organs in other annelids. 



In a careful account of this species by De St. Joseph (1894), he mentions that he 

 found on the branchiae Rhabdostyla arenicolas, Fabre Domergue. 



Fauvel (1899) considers the following as the young form in the abranchiate condition, 

 viz. Olymenides sulphured, Claparede, 2 De Quatrefages, Mesnil, and himself. He gives 

 somewhat later (the same year) an elaborate account of the three young forms which 

 Claparede and Mesnil considered as pertaining to a different genus, viz. Olymenides 

 sidfureus, 0. ecaudutus, and G. incertus, and decides that they are respectively only the 

 young of Arenicola marina, A. ecaudata, and A. Vincenti. The same author 3 has con- 

 tributed an account of the pigment in the group. 



Willem 4 (1899) describes the excretion in this species, treating first of the physio- 

 logical chemistry of chloragogenous tissue, then of excretions by amoebocytes in the 

 ccelomic . cavity, and lastly, of the structure and functions of the nephridia under the 

 heads of funnel, middle region, and terminal vesicle. 



Ash worth (1901) follows Benham's classification of Annelids, Arenicola being under 

 the Arenicolidse. He states that it contains two genera — Arenicola and Branch iomaldane. 

 This author examined the Arenicolidae in the Parisian Museum, and mentions an example 

 of A. marina with only eighteen bristled segments and twelve pairs of branchiae instead of 

 thirteen. 



The blood of Arenicola has again been examined by Peyrega 5 (1912), who finds that 

 the hemoglobin in it differs little from that in the horse. 



One of the most complete, as well as most recent accounts of this form and its allies, 

 has been given by Dr. Ashworth 6 (1912), who has made a special study of the Family, 

 and his excellent commentary on the notices by other authors has simplified the present 

 task. Moreover his careful investigation of the various types has enabled him to rectify 

 several errors in distribution and in structure. 



Caullery and Mesnil found E 'chinos ionium leptosomnm (a distome) encysted in Arenicola 

 marina. 



Sub-Family II. — Arenicolidde ecaudata, Johnston. 



Head (prostomium), simple, conical, non-lobate. Brain commissural. Statocysts 

 closed spherical sacs, statoliths spherical. Body almost uniform in diameter, without a 

 tail, as the feet and gills (which commence on the sixteenth segment) go to the posterior 

 end. Number of gills variable (according to age and species), unilaterally branched. 

 One pair of flask-shaped oesophageal pouches. Dorsal lip of segmental organs (the 



1 ' Zeitschr. f. wiss. Zool./ Bd. liii, Supply p. 217, Tab. xi — xiv. 



2 ' Bull. Sc. France et Belgique/ t. xxxii, p. 283, pi. iii. 



3 < Rev. Scientif.' (4), t. xiii, p. 54. 



4 'Observat. sur Pexcretion chez l'Arenicole/ 4to, Lille, 2 pis. •> 



5 < Compt. Rend. Acad. Sc./ t. cliv, pp. 1732—1734. 



6 ' Catalogue of the Chsetopoda/ A. "Polychseta." Part I, "Arenicolidae " : British Museum. 



