248 J- Playfair McMurrich, 



failed to giv^e ninety-six tentacles. The inner tentacles are markedly 

 larger than the outer ones, tlie latter being seated upon the margin, 

 biit all are of essentially the same shape, short and stout. with 

 roimded tips, in the centre of wliich there is in the niajority of 

 cases a marked depression, suggesting a Perforation. The inner 

 tentacles measured 0.6 cm in length and had a diameter of about 

 0.3 cm. The stomatodaeum is widely expanded and completely hides 

 the portion of the diso unoccupied b}^ the tentacles. Two rather 

 feebly developed siphonoglyphs can be distinguished and the walls 

 of the stomatodaeum are longitudinally ridged. Practically no traces 

 of color remains. 



Structure. The mesogloea of the column wall measures a 

 little more than 1 mm in thickness at the middle of the column 

 and has an almost homogeneous or in some places slightly flbrillar 

 ground substance in which numerous cells, sometimes arranged in 

 groups of two or three, are scattered. The circular musculature is 

 rather feeble, the processes for its support being low, stout and, for 

 the most part, unbranched. The mesogloeal sphincter (Fig. 31) is 

 developed in the upper part of the wall and is much feeblei' than 

 that found in other species of Adinostola. It is comparatively very 

 thin, though fairly broad, and lies close to the endodermal surface. 

 It is reticular in structure and presents no indication of layering, 

 resembling in this respect the sphincter Carlgren (1893) has described 

 for A. spefsbergensis. 



The longitudinal muscles of the tentacles and the radial muscles 

 of the disc are well developed and imbedded in the mesogloea. In 

 the tentacles branching laminae arise from the ectodermal surface 

 of the mesogloea and seem in individual sections to enclose portions 

 of the ectodermal epithelium (Fig. 32), although this appearance is 

 due solely to the manner in which the laminae are cut, the enclosed 

 epithelium of any section becoraing continuous at higher and lower 

 levels with the general ectoderm. No muscle cells could be disting- 

 uished in these apparent enclosures. 



The mesenteries are arranged hexamerously in five cycles, with 

 occasional representatives of a sixth, and the members of the first 

 and second cycles are perfect. There are two pairs of directives 

 attached to the siphonoglyphs, whose lower margins are prolonged 

 downwards as lappets almost to the base. In Fig. 33 is shown a 

 transverse section of a portion of the column in which is seen a 

 minute mesentery belonging to the sixth cycle adjoining a primary 



