RHOPALONEMA. 127 



different sizes, evidently of different ages (PI. 34, fig. U), and in all the 

 specimens all of them are broken short off. 



The club-shaped otocysts (PI. 34, fig. 13; PI. 45, fig. 10) have been well 

 described by Browne (: 04, p. 740, pi. 57, fig. 15). In a specimen 4 mm. in 

 diameter there are three otocysts each in six of the octants, and in the 

 smallest specimen apparently only one per octant. Vanhoffen (:02 b ) 

 records two otocysts per octant in an individual 3.5 mm. in diameter. The 

 manubrium is short and barrel-shaped, the mouth surrounded by four 

 narrow, pointed lips (PI. 34, fig. 15). The gonads, which are nearly spher- 

 ical, are attached to the radial canal only at a small area. This character, 

 clearly indicated in Browne's figures (: 04, pi. 57, figs. 11, 13), might easily 

 be overlooked on surface views on account of the small size of the gonads, 

 but is easy to demonstrate on serial sections. In the adult all gonads are 

 of about the same size, but in the small specimens small and large gonads 

 alternate, as Vanhoffen observed (: 02 b , taf. 10, fig. 18) ; but since in any 

 of our specimens all gonads are of one sex, this alternation is not con- 

 nected with hermaphroditism, as appeared to be the case in the specimens 

 described by Browne (: 04). 



The specimens were entirely colorless. 



Amphlogona apsteini is a surface form. It has previously been recorded 

 only from the Indian Ocean (Maldive Islands, Browne ; west coast of 

 Sumatra, Vanhoffen). 



Rhopalonema Gegenbaur, 1856. 

 sens. em. Vanhoffen (: 02 b ). 



Trachynemidae with thirty-two tentacles, of two kinds, i. e. radial clubs, 

 and inter- and adradial cirri; with enclosed otocysts; without peduncle. 



The above definition is that of Vanhoffen (:02 b , p. 59), who has shown 

 very clearly that the species of Marmema enumerated by Haeckel ('79), and 

 the majority, at any rate, of those of Trachynema, represent nothing more 

 than two successive stages in the development of Rhopalonema. 



The present collection contains two well-defined species of the genus, one 

 a surface, the other an intermediate form. The first of these is no doubt 

 identical with the species described by Vanhoffen (: 02'') and Maas ('93, :05) 

 under the name R. velaium Gegenbaur, and with specimens from the 

 West Indies in the Museum of Comparative Zoology. I believe that it is 

 also identical with the specimens from the Bay of Biscay identified by 



