36 THE MEDUSAE. 



Naitsithoe punctata is one of the most, if not the most, widely distri- 

 buted of surface Medusae. Unlike most other species it does not seem 

 to be limited by temperature, but has been found in the far north (Fewkes, 

 '88", Vanhoffen, : 02") as well as in various parts of the temperate and tropical 

 Atlantic, Indian, and Pacific oceans. 



Nausithoe rubra Vanhoffen. 



Nausithoe rubra Vanhoffen, : 02', p. 30, taf. 1, figs. 4, B. 

 Plate 12, Fig. 6. 



Station 4655 ; 300 fathoms to surface ; 1 specimen ; 15 mm. in diameter. 



Station 4633 ; 300 fathoms to surface ; 1 specimen; 10 mm. in diameter. 



Station 4672; 400 fathoms to surface; 1 specimen ; 18 mm. in diameter. 



Unfortunately all three specimens of this interesting species were in a 

 fragmentary condition, but still I am able to add somewhat to Vanhoffen's 

 (:02'') brief description. The bell is arched, a specimen 15 mm. in diameter 

 being 9 mm. high ; the ring furrow well marked, and the pedalia prominent 

 (Vanhoffen, : 02% p. 30). The marginal lappets, as Vanhoffen remarks, are 

 narrow and pointed, though, in view of the condition of the material it may 

 be questioned whether this is a constant character. 



The structure of the sense organs in this species is of great interest, since 

 it is no doubt an intermediate and not a surface form. In N. piitictata, as is 

 well known, each sense organ bears on the ventral bulbus an ocellus with 

 well-developed lens. In N. rubra, however, I was able to make certain 

 that on several well-preserved rhopalia there is no such structure. Each 

 sense organ, on the contrary, consists (PI. 12, fig. 6) merely of otocyst, 

 covering scale, and ventral bulbus ; and the latter, though somewhat pig- 

 mented, shows no more trace of any definite light-perceptive organ than is 

 to be found in Periphylla. This adaptation to a deep-water existence is even 

 more significant than the characteristic pigmentation of the species, to 

 which VanhijfFen (: 02% p. 30) has already called attention. 



The four septal nodes are broadly triangular, and so long that the gastric 

 ostia are narrow. The gastric cirri are rather more numerous than in N. 

 punctata, there being about one hundred in all. They are simple, and 

 arranged in single and continuous series along the four sides of the stomach. 

 Owing to the dense pigmentation of the entire ehdoderm, the peripheral 

 canal system is much more easy to follow than it is in N. punctata, with 

 which it agrees in all essentials. At the bases of the marginal organs the 



