A r en j co la cr is tat a 107 



neuropodia are absent on the first and usually also on the second 

 and third segments ; the neuropodia of the posterior branchial region 

 are long dorso-ventrally and almost reach the mid- ventral line ; six 

 pairs of nephridia, which open on the fifth to the tenth segments ; 

 one pair of oesophageal glands, conical, cylindrical or clavate, and 

 comparatively short ; a pair of large finger-shaped septal pouches ; a 

 pair of closed statocysts, each containing a single, large, secreted 

 statolith. 



HISTORICAL ACCOUNT. This species was founded by Stimpson to 

 contain some large examples of Arenicola collected by him on the 

 shore of Maurice Island, at the entrance to Charlestown Harbour. 

 He noted that in these specimens there were only seventeen chaeti- 

 ferous segments and eleven pairs of highly contractile gills, each 

 composed of twenty main axes bearing regularly arranged branches, 

 and that, on the tail region there were thick cutaneous processes. 

 He also recorded observations on the colours of the living animals, 

 and on the nature of their burrows and egg-masses. Stimpson's 

 description was apparently not known .to Liitken, who re-described in 

 accurate detail the external features of this species, under the name 

 of A. antillensis. Liitken drew special attention to the strikingly 

 pinnate character of the gills, which he believed to be so important 

 as to require the formation of a new sub-genus Pteroscolex for the 

 reception of this species. As is shown on p. 31 this sub-genus could 

 not be upheld, and has not been accepted by subsequent workers. 



The first record of, and observations on, examples of A. cristata 

 from the Old World, were those of Dr. Horst, who gave an account 

 of the gills and chaetae of Neapolitan specimens. Prof. Ehlers studied 

 the anterior end and statocyst, and Lo Bianco described the external 

 features and habitat of Neapolitan examples ; his Tav. I, Fig. 1, gives 

 a good idea of the colouration of the body, but the gills, which 

 are represented as being brownish, are usually a rich dark red colour. 



Prof. -Fauvel and Drs. Gamble and Ashworth gave accounts of the 

 anatomy ; and the admirable researches, first of Prof. E. B. Wilson, 

 and subsequently of Prof. Child and Dr. R. S. Lillie, have made 

 known the course of development of this species from the egg- 

 cleavage to the adult. 



OBSERVATIONS ON THE RECORDS.- There is no doubt that Stimp- 

 son's A. cnstata and Liitken's A. antillensis are the same species. 



