ANNELIDA PÜLYCHAETA. 39 



In the Gulf of Naples a species of Arenicola is to be 

 found , which in the number of its setigerous and bran- 

 chiferous segments agrees with our northern A. marina , 

 but in its other characters shows too much differences, to 

 be identified with this species. 



Claparède seems to have already presumed this, for he 

 writes: »une étude comparée plus approfondie ne révélera- 

 t-elle pas des differences spécifiques entre les individus de la 

 mer du Nord ou de l'Océan et ceux de la Méditerranée?" 

 However Levinsen has been the first, who considered the 

 Mediterranean specimens to be specifically different from 

 the northern form and named it A. Claparedi; he also 

 pointed out some characters by which this species is di- 

 stinguished from A. marina. 



The only specimen I could examine has a length of 

 75 m.m., the caudal region measuring 6 ni.m.; on the 

 contrary our A. marina attains sometimes a length of 

 250 m.m. This agrees with Claparède's statement: »mais 

 ce sont de véritables pygmées relativement aux Arénicoles 

 du Nord. La longueur moyenne des adultes mürs est de 

 six a sept centimetres." A. Claparedi resembles A. marina 

 in the presence of 19 setigerous segments, of which only 

 the posterior 13 are provided with branchiae; I do not 

 understand how Levinsen can write about this species : 

 »gjaeller findes paa 12 — 13 riuge", for all naturalists, 

 who examined this worm , agree with each other in this 

 point. It is true, Pennant 1 ) as well as Dalyell 2 ) have 

 figured A. marina only with 12 pairs of branchiae, but 

 we have no doubt that the drawer has overlooked the 

 first pair of branchiae on the 7th segment, which is much 

 smaller than the others ; for we read in DalyelPs descrip- 

 tion p. 136: » thirteen pair of beautiful vermilion branchiae 

 rise from the back." 



1) British Zoology; copied in the Encyclopédie méthodique, Vers, pi. 34, 

 ;. 16. 



2) The powers of the Creator, Vol. II. pi. XTX, fig. 1. 



Notes from the Leyden Museum, Vol. XI. 



