1888. J STRUCTURE OF CUTELLIO. 489 



in Peloryctes inqidlina the extent of the ditellum and the distribu- 

 tion of papillae is variable. I had fully developed sexual individuals 

 in which there was not a trace of cUtelluin ; all the area of segments 

 10-12 was covered with papillae like the rest of the surface of the skin ; 

 in others, on the contrary, either segments 9 and 10 or 10 and 1 1 were 

 devoid of papillae. In the anterior part of the body all the first three 

 segments were sometimes devoid of papillae, sometimes only the head. 

 Finally the last 10 or 11 segments were often without papilla3." 



It does not appear to me that these facts are necessarily opposed 

 to the view that Peloryctes inquilina is synonymous with Glitellio 

 ater. It is a well-established fact that the clitellum is variable in 

 its appearance ; and I have myself observed specimens of Clitellio 

 ater in which the clitellum was fully developed and without papillae, 

 or not developed and with papillae. The hinder end of the body in 

 my specimens was generally, if not always, devoid of papillae. 

 Claparede does not apparently mention this fact, but his description 

 of the species is very brief and incomplete. With regard to the 

 absence of the papillae on some of the anterior segments, I may 

 state that in my specimens the papillae commenced rather gradually 

 and that those upon the anterior segment were, at least in some 

 individuals, considerably smaller than the papillae of the following 

 segments ; this may perhaps account for the discrepancies between 

 Zenger's observations and those of Claparede. There may be 

 something in the structural diU'erences between the papillae of 

 Peloryctes inquilhia and those of 0. ater ; the papillae of the 

 former species are stated by Zenger to resemble very closely those 

 of Pachydrilus verrucosus. The setae oi Peloryctes inquilina are all 

 bifid, but they are alleged to differ from those of Clitellio ater in 

 the number per bundle — a character which I cannot admit to be 

 valid, as I have found great differences in this respect between 

 individuals of C. ater, and indeed of other species of Oligochaeta ; 

 it is, I think, recognized that in those forms with a large number of 

 setae in the bundle the number is variable. 



Another point which Zenger raises is the characters of some of 

 the transverse branches which unite the dorsal and ventral trunks 

 in some of the anterior segments. In the 7th, 8th, and 9th 

 segments of Peloryctes inquilina these trunks are specially dilated, 

 and this difference from other Tubificidae is regarded, in ton- 

 junction with the other points of difference, as sufficient to necessitate 

 the establishment of a new genus. The generic name is Leuckart's, 

 and was originally applied to Clitellio arenarius until the latter was 

 shown to be identical with Savigny's Clitellio arenarius; Zenger 

 therefore, and this proceeding of his will not be admired by those 

 who regard zoological nomenclature as a serious subject, resuscitates 

 the name Peloryctes to apply it to his species. 



In the examples of Clitellio ater which I studied I found it to 

 be by no means so easy as in Limnodrilus to distinguish any of the 

 vascular arches of the anterior segments as specially enlarged ; in some 

 specimens, however, the vascular arch of the 8th segment, as in 

 Tubifex, was decidedly stouter than the rest ; in other specimens this 

 difference was not so striking, and then the arches of G, 7, and 8 



