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



same of course holds good of the coronal pouches whose subumbral wall forms the folded 

 muscular arese. In the middle of the lower or distal margin of each coronal pouch, 

 just where its two lobe pouches opens into it, a canal also runs out from it between the 

 two lobe pouches which leads into the tentacle inserted in the coronal pouch. The four 

 interradial sense canals ("bursse sensillares," bo) which provide for the four sense clubs, are 

 short and simple, and swell into a spheroidal vesicle (" ampulla rhopalaris," oa ; PI. XIX. 

 figs. 2-3 ; PI. XXII. fig. 22 ; PL XXIII. figs. 31, 32, oa) at the basis of each sense club (on 

 the axial side). The formation of the twelve tentacle canals (of which four are perradial 

 and eight adradial) is more complicated. At the tentacle basis, below the two tentacle 

 roots, these canals can be closed by the peculiar double valvular vent-hole already de- 

 scribed (comp. p. 68, and PI. XXII. fig. 22, yk' , ex). 



These complicated anatomical conditions of the peripheric pouch corona are more 

 difficult to understand, inasmuch as each of the twelve tentacular coronal pouches (but not 

 the four ocular coronal pouches) are divided into two pouches by an imperfect tangential 

 septum (PL XXII. fig. 22 ; PL XXIII. fig. 29). These two pouches, the inner or axial 

 velar pouch (be), and the outer or abaxial avelar pouch (be'"), communicate by a lon- 

 gitudinal cleft in the middle of the septum which divides them ("fissura septalis," be'"). 

 This peculiar complication arises from each tentacle sending out above at its insertion 

 (between two marginal lobes) two diverging centripetal muscles, the root muscles of the 

 tentacles (mk) already described. These invaginate the lower or distal margin of the 

 coronal pouch in such a way that each tentacle root is surrounded by a conical 

 ectodermal hollow space, the funnel cavity of the tentacle root (it). The cascal end of 

 this funnel cavity extends to the upper or proximal margin of the coronal muscle where 

 the point of the tentacle root is inserted. The septal fissure, by which the axial velar 

 pouch communicates with the abaxial avelar pouch, remains between the two bifurcate 

 diverging tentacle roots (mk). The "septum velare" (wm), which itself is hollow and 

 separates the two pouches, has consequently a very complicated formation. It is formed 

 by two parallel lamellae of the velar fold, which only pass into one another above at the 

 proximal margin of the coronal pouches and at the two margins of the septal fissure. 

 The space between the two lamellae, the funnel cavity of the coronal pouch (" infundibulum 

 coronare," ic) is lined by the ectoderm of the subumbrella, and divided into a distal 

 simple " funnel cavity of the tentacle base," and two diverging cEecal horns running 

 proximally from it, the two "funnel cavities of the tentacle roots" (it). The muscular 

 wall of the delicate membranes which separate these cavities forms part of the iu- 

 vaginated coronal muscle, and is laid in delicate folds, as is best seen from the figure of 

 the partially-opened coronal muscle in Plate XXIV. fig. 1 . 



Genitalia ("sexualia," s ; PL XIX. fig. 6 ; PL XX. fig. 8 ; PL XXI. figs. 17 18 ; 

 PL XXII. figs. 38-40). The single specimen examined of Perijihylla mirabilis 

 was a mature male, whose testes had shed most of the spermatozoa. The testes 



