DESCRIPTIONS OF GENERA AND SPECIES 243 



This genus, which may be taken as the type of the family, has been principally 

 investigated by D'UDEKEM (6), CLAPARKDE (2, 3), VEJDOVSKY (24), MACINTOSH and 

 STOLC (3) ; these investigations relate entirely to T. rivulorum, the best known 

 species. The presence of capilliform setae in the dorsal bundles distinguish this 

 genus from many other genera of Tubificidae, such as Limnodrilutt, which has been 

 by some authors confused with it. Besides the capilliform and uncinate setae, the 

 first fifteen segments of the body contain pectinate setae much like those of Psam- 

 moryctes, but with the additional prongs less marked. Towards the end of the body 

 the capillifonn setae of the dorsal bundles disappear. The ventral seta bundles 

 contain only uncinate setae. The cerebral ganglia have well marked ' lateral lobes 

 arising anterolaterally ; posteriorly the brain is trifid with two larger lateral and one 

 smaller central division. 



A second species of the genus has lately been described by VEJDOVSKY (8) ; this 

 worm differs in several particulars from the type species of the genus; it is indeed 

 a little doubtful whether it is rightly included by VEJDOVSKY in the genus Tubifex. 

 The principal external difference is in the absence of capillary setae ; as, however, 

 these are wanting in the posterior part of the body of Tubifex rivulorum, the 

 difference is not perhaps so great ; besides we know that Hemitubifex may, or may 

 not possess capilliform setae in the dorsal bundles. The sexual orifices are stated by 

 the describer of the species to be exactly as in Tubifex rivulorum; according to his 

 figure, however, (8, PI. xv. figs. 2, 3) the male-pores are upon the tenth segment 

 instead of the eleventh, as in T. rivulorum; there is clearly no slip of the pen here, 

 for in the description of one of the figures (fig. 4), the author expressly mentions 

 the tenth segment as being that upon which the spermiducal glands open. Another 

 external difference from Tubifex rivulorum is in the presence of ' penial ' setae near 

 to the orifices of the sperm-ducts and spermathecae ; these exist in many Tubificidae, 

 but not in Tubifex rivulorum 2 . As to the form of these setae VEJDOVSKY is unable to 

 give any details ; the extremities were broken off. In other respects there are no 

 differences of more than specific value between the two species. 



As to the possibility of Ilyodrilus sodalis being a Tubifex, I refer to the matter 

 later. It differs from the other species, if it is correctly referred to this genus, in 

 having pulsating vessels, not dilated, in segments viii-x. 



1 This description is from VEJDOVSKY. 



" It must be remembered, however, that there is not certainly a difference here. VEJDOVSKY mentions that 

 the sexual setae of this worm were broken. Now in Tubifex rirc/orum there are the usual ventral setae at 

 the male pores as at the female pores ; it is quite possible, therefore, that the setae of T. blanchardi are merely 

 ordinary setae. CLAPAB{:DE (2, p. 23) refers to the existence of setae upon the segment bearing the male pores, 

 which are placed a little in front of the setae. I have found them to persist in a species from New Zealand, 

 which appeal's to differ in no way from T. raulurum (-T. boinieti). 



i i 2 



