184 OLIGOCHAETA 



(2) Aeolosoma quaternarium, Eheenbekg. 



A. quaternarium, Ehrenbekg, Symb. Phys., 1831. 

 A. venustum, Leidy, Journ. Acad. Nat. Sci. Philad. Vol. 11 (1850), p. 46. 

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

 Chaetodemus quaternarius, Czeeniavsky, Bull. Soc. Nat. Mosc. 1880, p. 307. 



Deflnition. Head equal in breadth to following segments. Setae sliarply bent ; those in 

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

 by deep fissure. Integumental globules orange-red. Oesophageal 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 Vbjdovsky to place 

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

 as synonymous with A. hempricliii. 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 ]py 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 formg,tion of cysts in A. hemprichii 

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

 other Aeoloso7na 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, Vejdovsky. 



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



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

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



