184 OLIGOCHAETA 



(a) Aeolosoma quaternarmm, EHRENBERG. 



A. quaternarium, EHRENBERG, Symb. Phys., 1831. 

 A. venustum, LEIDY, Journ. Acad. Nat. Sci. Philad. Vol. II (1850), p. 46. 

 A. italicum, MAGGI, Mem. Soc. Ital. Sci. Nat. Vol. I (1865), p. 8. 

 Chactodcmus quaternarius, CZERNIAVSKY, Bull. Soc. Nat. Mosc. 1880, p. 307. 



Definition. Head equal in breadth to following segments. Setae sharply bent ; those in 

 each bundle of the same length. Supraoesophageal ganglion divided into two posteriorly 

 by deep fssure. Integumental globules orange-red. Oe&ophageal segments without nephridia. 

 Intestine surrounded by a paired blood-sinus. The worm can temporarily encyst itself. 

 Localities England, Europe, N. America. 



This is quite a distinct species from the last, as will be seen on comparing the 

 definitions. A. italicum was incompletely, and possibly erroneously, described by 

 MAGGI. If correctly described in all particulars it should be referred to a distinct 

 species, characterized by having only one pair of bundles to each segment instead 

 of two pairs each bundle containing only ten setae. The small prostomium and the 

 small size of the worm are the chief reasons (I presume) which led VEJDOVSKY to place 

 it as a synonym of A. quaternarium. It is not clear why VAILLANT regards A. italicum 

 as synonymous with A. hemprichii. In MAGGI'S paper the 'eggs' of A. italicum are 

 described and figured. VEJDOVSKY suggested that these, being surrounded by a capsule, 

 were cocoons, but remarked later (9) that it was not certain whether the structures 

 in question weie really cocoons or encysted worms. That the latter suggestion was 

 probably correct was shown by myself (27), and by him (2). The cysts are usually regu- 

 larly spherical, rarely oval or of a more irregular rounded form. The cyst wall is of an 

 appreciable thickness and is in some specimens thicker than in others. The cysts were 

 found at the beginning of the cold weather. The formation of cysts in A. hemprichii 

 is perhaps hardly an additional argument for its identity with A. italicum, the only 

 other Aeolosoma in which they have been described. LEIDY'S A. venustum is only 

 distinguished from A. quaternarium, according to LEIDY himself, by its smaller size 

 and longer setae. These characters can hardly be considered sufficient. 



(3) Aeolosoma variegatum, VFJDOVSKY. 

 A. variegatum, VEJDOVSKY, SB. Bohm. Ges. 1886, p. 275. 



Definition. Head broader than following segments. Setae longer and shorter in the same 

 bundle, sharply bent. Siipraoesophageal ganglion only just divided by a shallow furrow 



