70 THE VOYAGE OF H.M.S. CHALLENGER, 



above the auditory club ; of these the unpaired (lower) eye looks inwards, the two paired 

 (upper) eyes outwards. 



The nervous system of PeriphyUa, like that of all the Peromedusse, is at present 

 unknown, and, unfortunately, in spite of repeated efforts, I was unable to make it out from 

 the single spirit-specimen examined. It requires fresh researches on living and specially- 

 prepared material. But considering the high stage of differentiation and perfection to 

 which the formation both of the muscular system and of the sense organs of our highly 

 developed Medusa has attained, we may assume that the nervous system is also fully 

 developed. This supposition is further justifiable from the fact that the closely-allied 

 Cubomedusse have a highly developed nervous system with centralised nerve ring, and that 

 the organs of sense show many analogies in the two orders. A nerve ring probably runs 

 in the coronal furrow as an important central organ, in immediate connection with the 

 four interradial sense clubs. A second nerve ring perhaps exists at the margin of the 

 coronal muscle, and possibly a third at the oral margin or the palatine ring. From the 

 large size of this Medusa, these important conditions might be explained by examination of 

 more perfectly preserved PeriphyUa treated with osmium and other such reagents. 



The subumbral umbrella cavity (" antrum," PI. XIX. fig. 6 ; PL XX. fig. 8 ; PI. 

 XXI. figs. 12-19) in our PeriphyUa, as in all Peroniedusse, is divided into two distinct 

 sections, the distal simple coronal cavity and the proximal cpiadrilocular funnel cavity, 

 the palatine ring forming the boundary of the two. The distal (lower or oral) coronal 

 cavity of the umbrella (" antrum coronare," fig. 19, he) is simple, shaped on the whole like 

 a hemisphere or truncated cone, and enclosed round by the corona of the umbrella ; it is 

 7 cm. in height by 12 cm. in diameter, opens below to the outside by the opening of the 

 umbrella and contains the oesophagus in its centre. The upper boundary of the coronal 

 cavity against the funnel cavity is formed by the palatine ring (" annulus palatinus," wp). 

 I give this name to the important subumbral boundary ring between the cesophagus and the 

 coronal sinus, in whose plane the four perradial palatine nodes are inserted into the wall 

 of the sinus. Four wide horizontal openings, the funnel openings (" ostia infundibularia," 

 fig. 18, if), leading from the coronal opening of the umbrella into the four interradial 

 funnel cavities (ii), are placed between the four palatine nodes. 



The funnel cavities (" infundibula ") are conical ectodermal invaginations of the 

 subumbrella into the central stomach. They correspond completely to the "funnel 

 cavities " of the Lucernaridae, but are much more strongly developed, and play a much 

 more important part. Whilst in Pericolpa and Perrpalma they only reach the boundary 

 of the central stomach and basal stomach (as far as the pyloric ring), in Pericrypta and 

 l'< riphylla they completely hollow out the conical tseniola and also pass above into the 

 basal stomach as far as its conical point, where the csecal ends of their cones touch in the 

 subumbral centre of the umbrella cone. Each infundibulum represents a sub-regular cone 

 3 cm. high and 4 cm. in diameter at the base, and is divided by the horizontal boundary 



