942 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [16] 



the face of the gelatiuous blocks already mentioned, while on the periph- 

 eral side are two strong muscles, which coalesce in the smaller part of 

 the tentacle, forming a large pari of its wall, but which divide into two 

 nuiscles on the base of the tentacular socle. Passing around the margin 

 of the corona of the disk, these two muscles are inserted under the high 

 coronal muscle {mus. cor. e.), which forms the marginal boundary of the 

 exumbral side of the disk. Both of these muscles, as well as the smaller 

 muscle on the side of the tentacle turned towards the center of the um- 

 brella, have a browu color in the conservative fluid (alcohol), in which the 

 medusse are preserved. 



Perhaps the most characteristic organs of the corona are the sense- 

 clubs and the gelatinous elevations upon which they are carried. 

 Strangely enough, of the five specimens observed by Haeck'el, and of 

 the examples which I have studied, only two have a multiple of the 

 number four in the number of these oi'gans. When we reflect how few 

 known instances among medusae there are which do not have this nu- 

 merical resemblance and relationship, the exceptions become even more 

 prominent. I believe, however, that this departure from the normal 

 number is without morphological significance. The sense-bodies are 

 long, narrow, borne upon the members of the external zone of gelati- 

 nous blocks {soc. tib.), and are of the same number as the tentacles. 

 The bases of these organs are cubical or quadrangular pieces of trans- 

 lucent gelatinous character, with flat lateral faces and slightly curved 

 u[)per face. In alcohol the distal ends are bow-shaped, curved down- 

 ward. On each side at the free extremity there is a flat leaf-like ap- 

 pendage or patagium {mg. Ip.), in the angle between which lies the sense 

 bull). In most of the specimens the sense-bulb, although poorly pre- 

 served, is well developed and prominent, while the hood is inconspicu- 

 ous or wholly absent. The i^atagia were neither as broad nor as long as 

 in the closely allied Wyvillii, where, according to Hjeckel, they are in 

 the specimens which he studied '• invariably torn and badly preserved." 

 1 was unable lo trace the tubes from the chymiferous system of vessels 

 into the sense-bodies, although they probably have the same course and 

 general character as in the species Wyvillii. 



iSubumbrella. — The subumbrella is more complicated in its structuic 

 than the exumbrella, and from it hang several important structures. 

 The tentacles, which, in a majority of Acras])edote medusa^-, belong to the 

 appendages of the subumbrella and their homologues, the sense- clubs, 

 have been pushed around the margin of the corona to the exumbral side 

 by the great development of a circular muscle {mus. cor. e.) already 

 mentioned, as seen in part on the exumbral side, and which forms a 

 large portion of the margin of the subumbrella. Within this large 

 peripheral muscle, which is couiposed of a number of parallel layers, is 

 a second smaller and concentric thin circular nniscle {7nu.s. cor. i), the 

 inner edge of which forms the inner rim of the corona. In the species 

 ]Vi/v(lUi^ according to Hteckel, "the subumbrella is divided iu the 



