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



ao-e ; its total length amounted to 3 "2 cm., of which 2-0 cm. belong to the body, and 

 1'2 cm. to the foot. The former is on one side crushed inwards about the middle, 

 where it is of the greatest diameter (2 cm.), while on the other it is as strongly swollen 

 out. Above, it diminishes gradually into the head region, which is indistinctly 

 furrowed radially ; and below, equally gradually, into the foot. The latter is 

 cylindrical, and has a diameter of 0"5 cm., while the sole-like clasping-disc has at its 

 base a breadth of 0'9 cm. The third and still younger polyp consists mainly of the 

 ' body,' which above is flat and discoidal, without differentiation of a head-region, but 

 is at the periphery pressed into folds ; its height is 2 - 4 cm., its breadth 2"0 cm. Below 

 it passes gradually into the foot, which is rudimentary, round, only a few millimetres 

 high, and ends without a clasping-disc. 



" For investigation I made use of the middle specimen, which was completely 

 preserved. A longitudinal section dividing the polyp into two halves yielded the 

 following results. The mesenteries run in the foot as clear narrow ridges on the body- 

 wall, scarcely projecting into the interior ; they extend also on to the horizontal pedal 

 disc, and appear in this region as radiating lamellae, which meet at the centre of 

 the flat base. The filaments first appear on the mesenteries at the point of transition 

 into the broader '_body ; ' they form a thick investment, which nearly fills the whole 

 ccelenteron and covers the mesenteries completely. The body-wall is fairly thick, and 

 even with the naked eye can be distinguished into two layers ; an outer, which appears 

 granular owing to the accretions, and an inner, which is soft, shining, and free from 

 deposits. It is further noticeable, that the quantitative relations between the incrusted 

 and the softer layers vary with the height of the part in question, and in such a 

 manner that, at the upper part of the body, both parts are about equally strongly 

 developed, while with increasing depth the harder constituents become more numerous, 

 till at last, in the foot, a complete obliteration of the softer zone is produced. Above, 

 the body-wall is drawn rather deeply inwards at a sharp angle. On to this infolded 

 region the accretions are uninterruptedly continued as far as the point of origin of the 

 oral disc, the latter being inserted just at the inner edge of the fold. The stomatodseum 

 reaches far downwards, and is characterised by a siphonoglyphe of considerable depth. 



" A transverse section in the region of the stomatodaaum allows the mesenterial 

 arrangement to be recognised even by the naked eye. The longitudinal section having 

 been carried midway between two mesenteries on both sides, they were completely 

 intact, and the combination of the two sectional halves yielded a complete picture of 

 the mesenterial arrangement, which falls under the microtype. Sixty mesenteries in 

 all are present ; of these, after deduction of the regularly formed dorsal pairs, there fall 

 into the ventral zone on each side of the directive macromesenteries, twelve pairs, 

 consisting each of a macro- and a micro-mesentery. 



"For a study of the anatomical relations in more detail, I made use of von Koch's 



