H. F. NIERSTKASZ. 



the name Proneomenia discoveryi* is related. In the first place we must mention the 

 different forms, which are now considered as belonging to the genus Proneomenia. The 

 thick cuticle with the needle-shaped spicules, the polystichous radula, the two tube- 

 shaped salivary glands, and the absence of gills point towards a relation to that genus. 

 The genus Proneomenia includes at present no less than fourteen species, viz., sluiteri 

 Hubr., acuminata Wir., vagans Kow. a. Mar., desiderata Kow. a. M.&r.,gorgo)wphila Kow. 

 a. Mar., weberi Nierstr., longa Nierstr., thulensis Thiele, valdiviae Thiele, australis 

 Thiele, amboinensis Thiele, gerlachei Pels., liawaiensis Heath, and neapolitana Thiele. 

 As already mentioned by me (8), the expression " polystichous" radula has to be taken 

 in a wide sense, as very different types belong to it, which must lie kept sharply 

 separated. The salivary glands likewise show remarkable differences. 



All the above-named forms have a thick cuticle beset with numerous needle- 

 shaped spicules. This characteristic, however, is not typical of Proneomenia, but also 

 holds good for other genera, e.g., Rhopalomenia. The length-index varies considerably, 

 from 6 (P. desiderata) to 50 (P. longa). 



Epithelial papillae are of general occurrence ; however, they are said to be 

 wanting in Proneomenia sluiteri, though represented and described by Heuscher for 

 P. langi. On studying Hubrecht's sections of sluiteri more closely, I came to 

 the conclusion that epidermal papillae really are present in this form. In the 

 outer part of the cuticle many of these papillae are found, just as Heuscher observed 

 them in langi (3, p. 3). Owing to this fact another point of difference between the 

 two forms disappears, and we have the more reason to share Thiele's opinion, and to 

 consider both forms as belonging to one species (17, pp. 261). 



All the forms of Proneomenia have one or more dorso-terminal sense-organs. 



The structure of the coelomoducts (cloacal ducts) and their appendages varies 

 considerably. The latter always occur at the point where the proximal directed part 

 of the coelomoducts bends to take a distal direction. Proneomenia sluiteri shows 

 glandular, ramified tubes ; langi, winding coeca ; weberi, longa, acuminata and gerlachei, 

 one vesicular appendage ; thulensis, twenty, often lobate vesicles ; valdiviae, a tube ; 

 australis, thirteen stalked vesicles. 



The abdominal and cloacal spicules (abdominale Hakenbiindel und Kloakcnspicula, 

 Thiele (13, p. 291) ) show also important points of difference : sluiteri, langi, 

 desiderata, gorgonophila, weberi and longa have the so-called abdominal spicules in 

 great numbers. Thiele found their homologon in vagans and australis (13, p. 261 ; 

 17, p. 256). In longa they even are numerous, though of smaller size. In 

 discoveryi two complicated copulation-spicules likewise are present, which show affinity 

 to those of vagans and to the penis-spicules of Neomenia. 



Regarding the cloaca, we must observe that gills are always wanting, the gills of 

 the Solenogastres being merely folds of the cloacal epithelium. It is a very remarkable 

 fact that they are absent from all species of Proneomenia. 



* Sit venia verbo ; we have a precedent in CJiallengeri.'En. 



