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



five small ones, and three wart-shaped and undeveloped. The terminal polyp was 

 bent in such a manner that it lay apparently at the dorsal side of the two ujDpermost 

 lateral polyps. Then succeeded three well-developed lateral polyps on the right side, and 

 on the left only one smaller. The dorsal polyps were six in number, five of which had 

 tentacles, but were small, the sixth being only rudimentary. Other two rudimentary 

 polyps were placed at the ventral side of the right lateral lower individuals. 



The best developed polypidom of all (fig. 37) showed in the middle on its ventral 

 side the terminal polyp in which the axis was not visible with the exception of its end. 

 Two large lateral polyps appeared on both sides, and between these and the terminal 

 individuals, but on the ventral side of the lateral, five young polyps and a rudimentary 

 one, the position of which is well shown by the figure. On the dorsal side four pretty 

 well-developed polyps lay between the lateral ones, two larger in the middle, one above 

 the other, and two smaller at the sides. Besides these, two very small polyj^s were 

 situated between the left dorsal, the left lateral, and the terminal polyp, and two rudimen- 

 tary ones at the same place on the other side. 



Taken altogether, we may say that in the younger specimens the polyps show 

 a regular bUateral arrangement. A terminal and two lateral polyps are the first 

 expression of it. Then new buds arise, first on the dorsal, and then on the ventral 

 side, and these are in part also decidedly bilateral. But such buds seem likewise to grow 

 on the dorsal middle line, which fact would alter the symmetry. It may, however, be 

 supposed that these are also in reality lateral, and that the polyps of UmheUida are essen- 

 tially disposed in series on both sides of the rachis, which arrangement is veiled by 

 the shortness of their seat of attachment. 



The polyps of Umhellula huxleyi are dark brown in their upper parts and lighter 

 below; they have the tentacles shorter than the bodies of the polyps, and regularly beset 

 with short jjinnulse. A peculiar fact which was new to me is, that these polyps are 

 retractile, but this retraction takes place very seldom, and was only to be seen in one 

 specimen. 



The stalk is somewhat rich in sarcosoma, especially at its enlargements, and shows 

 only faint traces of colour, both ends being pale. Its most remarkable feature is the 

 arrangement of the zooids, which are most numerous on the upper enlargement, which 

 they cover on every side, with the exception only of the dorsal and ventral middle line. 

 From this point, the zooids throng to the polypiferous portion and pass on to the 

 terminal polyp nearly as far as the axis, whilst they end at the bases of the other polyps 

 entering for a certain distance in the sjsaces which sej)arate them. In the interior of the 

 bunch of polyps no zooids are present. 



The zooids just mentioned are visible to the naked eye, but the microscope is required 

 to ascertain that, as in the Umhellula gUntheri, they are also present on the remainder of 

 the stalk and even on its lower enlargement. As far as I could ascertain without destroy- 



