South- American Tubificidse. 207 



(2) The presence of two seti« only in cacli ventral bumllc, 



of wiiich one is uncinate, the other simple. 



(3) The opening of" the s[)ennnthecie in segment xiii, behind 



the male pores. 



(4) The fact that the .sperm-duct opens independently of 



the spermiducal gland into the penis. 



Tliis combination of characters occurs in no other Tubiticid. 

 In fact more than one of the characters is j)ecLiliar to the 

 present genus. The curious arrangement of the ventral setaj 

 is peculiar, and so is the position of the sperinathecai. 



It is the rule among the Tubificidai for the sperm-duct to 

 open into the extremity of the spermiducal gland, which has 

 ordinarily the appearance of being a continuation of it. To 

 this rule there has hitherto been only a single exception 

 recorded. This exception is the remarkable genus Bran- 

 chiura *, in which the sperm-duct opens into the lowest part 

 of the spermiducal gland just before the latter becomes con- 

 tirnious with the penis, in Il'isperodrilas the same state of 

 affairs is met with, but the gland is not enveloped, as it is in 

 Branchiura^ by a thick outer coating of glandular cells ; tliere 

 is only the lining of cells, which are, however, extremely 

 glandular ; the distinct prostate found in so many TubificiJai, 

 but wanting in Branch in ra, Clitellio, and [///odrilus, is also 

 wanting in Uesperodrilus. As to the peculiar condition of 

 the sette of the ventral bundles, it might perhaps be thought 

 that there is some error ; it is so frequently the case that one 

 of the teeth of the bifid seta is worn. In the present instance 

 there can, I think, be no doubt about the matter ; the two 

 kinds of setae occurred with far too great a regularity to admit 

 of any such explanation as that suggested. 



The follo\ving is a brief description of the main characters 

 of the four species belonging to this new genus : — • 



1. Hesperodrilus branchiatus, sp. n. 



I refer first to this species on account of its interest in 

 being another branchiate species. This is now the second 

 Tubiticid in which organs clearly of a branchial nature exist. 

 The other species is Branchiura Soiverbii, which I discovered 

 two years ago in the " Victoria re(/ia " tank at the Botanical 

 Society's Gardens in the Regent's Park. At first I naturally 

 supposed that I had before me an example of that worm, the 

 habitat of which is very possibly South America ; but in tlie 



* '' A uew Brauohiate Dlifrochaete, Brtmchinrd SowerMi," Q'lart" 

 Journ. Micr. Sci. 189J, p. l. 



