A NEW FRESI I- WATER NEMERTINF. 



247 



question with regard to their excretory organ, their rhynchocoel, and 

 very probably, to their rhyncho stomodauim and hermaphroditism as 

 well. However, upon finding some incongruous points in Montgomery's 

 definition of Stichostemma when applied to the two species, St. asen- 

 soriatmn and gracense, Böhmig (1898) has revised the generic dia- 

 gnosis as follows : 



"Augenzahl veränderlich, gewöhnlich mehr als 4 ; 9 oder 10 

 Rüsselnerven ; das Rhynchocoelom erstreckt sich nicht bis an das 

 Körperende ; die Nephridien dehnen sich von der Gegend des Gehirns 

 bis zur hinteren Körperspitze ; zwitterig, ovipar." 



I take this definition of Stichostemma to be excellently drawn 

 up, sharply differentiating, as it does, that genus from the other. No 

 emendation to it is made necessary by the discovery of the new 

 species described in this paper. 



On the following page is given a tabular list of the more important 

 characters of the three hitherto known species and of the present new 

 species of Stichostemma. 



A glance at that table will show that the present species is 

 more closely related to St. eilhardi than to any other of the species, 

 and that St. asensoriatum takes an isolated position in that it lacks 

 the frontal organ and is provided with an indefinite number of eyes. 

 The relation between the present species and St. gracense, in spite 

 of several points of agreement in internal anatomy, seems to be 

 comparatively remote, since the two species differ markedly from each 

 other in size and colour of body, in the presence or absence of senso- 

 ry spines, in the extent of cephalic glands, etc. With respect to the 

 last-named organ, the present species bears a singular resemblance to 

 the otherwise remotely allied member, St. asensoriatum. It is also a 

 noticeable fact that the present species shows, as regards the number 

 of proboscis-nerves, an intermediate or transitional relation t:> the 

 three other species. As already stated in the foregoing description, 

 the said nerves number 9 or 10 in the present species, the variation 



