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



Each fold is formed by an elevation of the supporting lamella (2), which again forms 

 secondary folds, and therefore appears dendritically branched in transverse section. 

 The circular fibres of the muscular plate (m) cover this system of folds connectedly ; and 

 are covered in their turn by the ectodermal epithelial cells of the subumbrella (qw) from 

 which they are secreted. The eight longitudinal deltoid muscles (figs. 2, 3, 4, 12, md) 

 work antagonistically to the eight circular marginal muscles. In the deltoid muscles of 

 our species the four perradial (md') are very weak but very broad, whdst on the other 

 hand the four interradial (md") are much narrower, but proportionately more strongly 

 developed. These appear to be the direct processes of the strong tseniola muscles, 

 they run along the entire length of the septa of the pouches (fig. 12, tr.s), and split up 

 below at the distal end of the latter, into two strong limbs (fig. 12, md'") each of which 

 bears a bunch of tentacles. 



The umbrella margin has eight shallow concave depressions or " marginal sinuses," 

 between which, as in all Lucernaridse and Pericolpidse, lie eight adradial marginal lobes. 

 These eight adradial hollow marginal appendages, which have hitherto been generally 

 termed "arms" in the Lucernaridse and erroneously considered a special peculiarity of this 

 family, are, in fact, from their situation, structure, and signification, merely the eight 

 adradial marginal lobes of the closely allied Pericolpidae and as such homologous to the 

 eight sense lobes (or "eye lobes") of the Peiiphyllidae. The essential difference from 

 the Pericolpidas, which is strikingly displayed by the Lucernaridse, is that each of the 

 marginal lobes or " arms" bears a brush-shaped bunch of numerous small, hollow 

 knobbed tentacles at their points. Morphologically considered, these tentacles belong to 

 the category of accessory or secondary tentacles, and are merely long-stalked urticating 

 knobs. On the other hand the four principal tentacles of Tessera (four primary perradial 

 and four secondary interradial) have disappeared in the genera Lucernaria and Cratero- 

 loplms, whilst in Haliclystus and Halicyathus they are transformed into adhesive 

 " marginal anchors." In our species the eight arms are very small, and less developed 

 than in most other Lucernaridas ; they project only slightly from the umbrella margin 

 as broad triangular points and are placed together in pairs, so that the four perradial 

 sinuses of the umbrella margin are three times as large as the four interradial (figs. 1-4). 

 Each short arm or marginal lobe bears a bunch of from 80-120 tentacles. 



All the tentacles (PI. XXII. figs. 15, 16) are completely fused together at their 

 basal halves, so that only their distal halves are free and movable (fig. 15). They 

 are cylindrical, 2-3 mm. long, when contracted (probably twice as long when extended), 

 and nearly \ mm. thick. As in all true Lucernaridse, they are hollow, thick-walled little 

 tubes, whose csecal and somewhat thinner distal end bears a thicker urticating knob. 

 This stalked urticating knob in our species is developed into a strong sucking-cup, with a 

 depressed sucking-pit in the middle (fig. 16, x). The hollow cylindrical epithelium of the 

 ectoderm (q) is four to six times as high in the sucking-cup as on the tentacle stalk, and 



