38 THOS. H. MONTGOMERY, 



stemma, namely that the nephridia extend from the head, in front of 

 the brain, to the very posterior end of the body^). The nephridia 

 of Stichostemma are thus the longest known in any Xemertean, being 

 longer [than in Eunemertes and Nemertopsis (cf. Bürger, '95 b) and 

 in 'Prosorhochmus{"'Tetrastemma''') ohscurus, according to Max Schultze 

 ('51); it is remarkable that BtjRGER, in his recent monograph, has 

 not referred to the nephridia of Schultze's species. In my opinion, 

 the structural differences mentioned in my previous paper, furnished 

 reasons enough, not to assign St. eilhardi to the genus Tetrastemma; 

 and the addition of the remarkable differences in the nephridia, may, 

 I hope, convince the distinguished Göttingen investigator, that Sticho- 

 stemma should not be united with Tetrastemma. I define the twa 

 genera then as follows: 



Stichostemma mihi: eyes variable in number, usually more than 

 4; 9 nerves in the proboscis; rhynchocoel does not extend to the 

 posterior end of the body; nephridia extending from in front of the 

 brain, to the posterior end of the body; protandric, hermaphroditic, 

 oviparous. 



Tetrastemma Ehrenb. : eyes not variable in number, either 4 

 single eyes (the rule), or 4 double eyes {T. falsum, cruciatum); 10 

 nerves in the proboscis ; rhynchocoel extends to the posterior end of 

 the body; nephridia not extending posteriorly behind the oesophagus; 

 dioecious, oviparous. 



In my critical bibliography of the freshwater Nemerteans ('95 a), 

 I showed that Dugès' species Prostoma clepsinoides and P. lumhri- 

 coides, being so insufficiently described as to be unrecognizable, are 

 untenable; but Bürger ('95b) while disregarding the doubtful Emea 

 rubra Leidy, which is, however, more fully described than Dugès' 

 species, accepts the latter as good species of Tetrastemma: this method 

 of dealing with questions of nomenclature, after they have been more 

 fully discussed by a previous author, is to be deprecated. Bürger 



1) Further, the wall of the nephridia is formed of a flattened 

 cubical epithelium, in which the separate cells are scarcely distinguish- 

 able, and not by a cylindrical epithelium, with clearly marked cell 

 walls, such as I find in Tetr. vermiculum, and as Büeger ('95 b) has 

 described for the Metanemertean nephridium in general. In one indi- 

 vidual I find 19 excretory pores on the right side and 16 — 19 on the 

 left, 4 on each side being placed below the nerve chord. For further 

 details on this interesting nephridium, I must refer to a later paper,^ 

 to be pviblished in the next number of this journal. 



