38 THE VOYAGE OF H.M.S. CHALLENGER. 



Leiotealla nymphaia (PL VII. figs. 1-5). 



Actinia mjmphcea, Drayton, in Dana. Expl. Exp., Zooph., p. 14G,pl. iv. fig. 33 (Synopsis, p. 10), 



1846. 

 Paradts (?) ni/r7iph(ea, Milne-Edwards, Hist, des Corall, torn. i. p. 252, 1857. 

 Sagartia (?) nympluea, Verrill, Tran.s. Connect. Acad., vol. i. p. 486, 1871. 



Tentacles short, in three rows, body constricted half-way up Ijy a special circular 

 muscle, insertions of the septa shining through the wall as longitudinal lines. 



Habitat. — Station 149. Christmas Harbour, Kcrguelen. January 29, 1874. 

 Depth, 120 fathoms. One specimen. 



Dimensions. — Height, 1 cm. ; breadth of the base, 2 cm. 



This small Actinia, of which there was only a single specimen, was examined in a 

 strongly contracted condition. The oral disk was completely inverted, and the margin of 

 the peristome drawn over it, so that only a narrow passage was left ; at two-thirds of the 

 height the body showed a circular constriction, caused, as we shall see, by a special 

 muscle, which is wanting in most Actiniae. 



The surface of the body in Leiotealia nymphcea is perfectly smooth, and so thin that 

 the origins of the septa, which number more than a hundred, shine distinctly through it, 

 in the form of white lines. Muscular fibres are present only on the endodermal side, 

 and form a smooth layer, which, from the contraction of the animal, was only slightly 

 pleated, though it was thickened at two places into distinct sphincters. The upper 

 sphincter is the more powerful, and corresponds to the sphincters of other Actiniae in its 

 position, immediately under the margin of the peristome, and in its action, for like them it 

 draws the wall together like a bag'; it is a circumscribed muscle, and projects into the 

 stomach as a circular swelling, which is only fastened to the w-all by a narrow base, and 

 pierces the origins of the septa. Seen in transverse section (PI. VH. figs. 2 and 4) 

 a process of the supporting lamella of the wall makes its way into the inside of the 

 swelling, and traverses it nearly to the opposite end ; it thus divides the swelling into 

 two parts, the upper being about three times as broad as the lower, which pass into one 

 another at the free end of the process. Unless the section passes through the precise 

 point where the sphincter pierces the septum, each part shows on the surface a layer of 

 epithelium, and inside the repeatedly folded muscular lamella, supported by very fine 

 folds of connective tissue. The folds of connective tissue spring from the axis of 

 connective tissue, and throw out irregularly several lateral branches, all equally covered 

 with muscular fibrilla3. The spaces between the folds of connective tissue are open 

 towards the epithelium, so that the latter passes in between them. The lower ends of 

 the pleatings of the muscle are rarely detached, so as to form flat mesodermal bundles of 

 fibrillse ; this takes place more frequently at the free end of the axis of connective tissue. 



The lower circular muscle (figs. 2 and 5, ms') is less highly developed ; to the naked 

 eye it shows as a narrow palish-yellow tract, running upwards and downwards ; seen 



