10 JOSEPH A. CLUBB. 



what justified in this course, although I agree that it will be better to adopt 

 Carlgren's proposal, and include such forms under the genus Rhodactinia, and reserving 

 the genus Urticina or Tealia for species where the radial muscles of the oral disc 

 and the longitudinal muscles of the tentacles are always completely imbedded in the 

 mesogloea. 



In the ' Discovery ' collection are six specimens, all taken at the Winter 

 Quarters, McMurdo Bay, in from 10 to 20 fathoms, and bearing the following dates : 

 20. 2. 02 ; 17. 1. 03 and 17. 2. 04. They are all of large size, the largest being 

 6 5 cm. in height of column and 6 cm. in diameter of oral disc. The external 

 appearance of these specimens varies considerably, according to the degree of con- 

 traction of the oral disc or body-wall. I have had under observation for some time a 

 number of specimens of crassicornis from Hilbre Island, living in one- of the tanks of 

 the aquarium of the Liverpool Museum ; they are all in a flourishing condition and 

 feed voraciously. I have been surprised to note their extreme mobility. Tentacles, 

 oral disc and body-wall exhibit remarkable degrees of inflation, sometimes all together, 

 sometimes singly, and sometimes only sections of each of them. In extreme dilation 

 of the body-wall all trace of verrucas, as such, is lost, and as Teale (11) observes, it 

 " renders the corium perfectly smooth, so that the small opaque spot alone indicates 

 their former situation." Correspondingly, in extreme dilation of the oral disc, the 

 tentacles may be so reduced as to be little more than papillae. On PI. 3, Fig. 22 is 

 a reproduction from a photograph of the oral disc of a living animal, which well 

 illustrates this extreme contraction of the tentacles. On the other hand, I have 

 recorded specimens where the tentacles have measured 4 5 cm. in length and 6 cm. 

 in diameter near the base. There is always general expansion, especially of the 

 tentacles after feeding. McMurrich (9, p. 28) discusses this great variation in external 

 appearance brought about by this great mobility, and the internal anatomy, sphincter, 

 muscles of the tentacles, mesenteries, and body-wall and other internal structures 

 must correspondingly vary, according to the degree of contraction or expansion. 



In all the ' Discovery ' specimens under consideration the radial muscles of the 

 oral disc and the longitudinal muscles of the tentacles are meso-ectodermal, and in 

 contraction are identical in appearance with the figure given by Carlgren for his 

 variety spitzbergensis (2, Fig. 3, p. 41). The sphincter is endodermal, and strongly 

 circumscribed, and may be seen in all cases by the naked eye when the parapet is cut. 

 Transverse sections show a little difference in detail in the arrangement of the 

 mesogloeal processes, whereas in some the more typical bipinnate arrangement is seen, 

 in others the plan is similar to the figure given by Kwietniewski (7, p. 14, Fig. 8), 

 for his Leiotealia spitzbergensis, which Carlgren (2, p. 40) now regards as a synonym 

 of R. crassicornis. I give a figure of this form of sphincter drawn from a section of a 

 ' Discovery ' specimen (PI. III., Fig. 23). 



As regards the verrucse, tentacles, oesophagus, siphonoglyphs, directives and 

 other mesenteries, and in other anatomical features, the specimens under consideration 



