THE MEDUSAE OP THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 179 



base. VANHOFFEN places three species in the genus, the two old ones, D. pendula 

 from Tierra del Fuego, D. gaudichaudi from the Falklands and from near Cape Horn, 

 and a new species called D. chierchiana found at Punta Arenas in the Straits of 

 Magellan. This last species has been fully described and well figured, but I am able 

 to add a further account after the examination of five specimens in different stages of 

 development found in Stanley Harbour, Falkland Islands. It will be noticed that the 

 above three species are inhabiting the same region, and I have but little doubt that 

 they all belong to one species, which, in accordance with the law of priority, should be 

 called Desmonema gaudichaudi (Lesson). 



The description of Chrysaora gaudichaudi by LESSON is incomplete, and is based 

 upon an abnormal specimen with twelve groups of tentacles instead of the normal 

 eight. Consequently the shape and size of the marginal lobes would differ from those 

 of the normal type. AGASSIZ'S description of Couthouyia pendula is practically a 

 generic one, but he does state that the oral arms are of an extraordinary length. 



VANHOFFEN points out that Desmonema chierchiana is distinguished from 

 D. gaudichaudi by shorter oral arms. The largest specimen in the Scotia collection 

 shows that D. chierchiana has much longer arms than those mentioned by VANHOFFEN. 

 The length and size of the oral arms are of little use for a specific character, on account 

 of their great power of expansion and contraction. VANHOFFEN also points out that 

 the shape and size of the marginal lobes of D. chierchiana differ from those of 

 D. gaudichaudi. It must be remembered that LESSON'S specimen was an abnormal 

 one. The marginal lobes of the Scotia specimens are not quite like those of 

 VANHOFFEN'S Punta Arenas specimens, the difference being probably due to variation 

 and not to a different geographical race. 



VANHOFFEN lays a certain amount of stress on the gonads of Desmonema being 

 smaller than those of Cyanea, and not hanging down so far. The largest specimen in 

 the Scotia collection has much larger gonads than VANHOFFEN'S specimen, and they are 

 just like the gonads of Cyanea capillata. 



I rather think that the specific character of D. chierchiana lies in the arrangement 

 of the tentacles in practically a straight row, adjacent to the distal edge of the 

 circular muscles. Concomitant with the straight row of tentacles are the undivided 

 tentacular lobes, and the absence of radial muscles in the marginal lobes. The 

 tapering of the oral arms may also come in as a useful aid for the determination of 

 the species. The ultimate fate of Desmonema as an independent genus depends upon 

 the revision of the genera and species of the Cyaneidse. MAAS (1904) has also com- 

 mented upon the relationship of Desmonema and Cyanea, and the necessity for a 

 revision of the species. 



(ROY. soc. EDIN. TRANS., VOL. XLVI., 243.) 



