Earthicorvrs of the Vunna Mufteiim. 125 



rior 011(1 of tl.o atrium in tlie cigliteentli sei^mcnt ; it is ratlier 

 loni:; iinil coilrd, and opens on to the exterior witliout any 

 terminal dilatation. The structure of the atria is thus very 

 interesting;, inasmuch as they present us witli cliaracters 

 intermediate between the " lobate " and " tubular " form of 

 atrium. As both forms of atria arc met with in the Pcricha3- 

 tidje, lhou<;h the lobate is the more common type, the inter- 

 mediate condition is required. 



Close to the point where the atrium perforates the body- 

 wall on its way to the exterior is a sac containing penial 

 sctffi. These setaj differ (see fig. 13) from tliose of Merja- 

 scolc'x armatu.f, the only other species of the genus in which 

 they have been hitherto figured. They arc sharply bent at 

 the extremity, which is beset for a short distance with minute 

 dentieulations. 



Corresponding to the papillre which I have referred to in 

 describing the external characters are four round white glands. 



"Perichccta hrachycyda,'^ Schm. 



This is also a Megascohx ; there is nothing but the colour 

 to distinguish it from Megascolex cingulatus^ since the clitellum 

 was undeveloped, and since 1 have not been able to compare 

 the internal organs. As there is the colour difference I shall 

 for the present assume the distinctness of the species, and 

 rename it 



(5) Megascolex brachycyclus (Schm.). 



PericlKBta hrachycycla, Schmarda, Neue wirbell. Thiere, Bd. i. Half te ii. 

 p. 14. 



Megascolex Irachycyclus, Vaillant, Anneles, p. 88. 



The characters upon which Schmarda relied to distinguish 

 the species from the others described by him was the form of 

 the setje ; it is now known that the form of the setse cannot 

 be relied upon for the discrimination of the species of Peri- 

 chceta. This is certainly my own experience, and Prof. 

 Bourne, wdio has examined a large number of species, remarks 

 that, except in special cases, the shape of the sette " is of little 

 use for classificatory purposes." 



The dorsal and ventral gaps in the circles of setee are not 

 perhaps so well marked as in M. cingulatus. 



The first dorsal pore is, as in that species, between seg- 

 ments v./vi. 



The oviducal pores are double. 



The male pores are upon the eighteenth segment ; in front 

 of and behind each of them is a genital papilla ; these lie, as 



