148 REPORT ON THE PENNATULIDA. 



clothing it ; they are also devoid of spicules (Fig. 5). These partitions 

 are, so far as we have been able to determine, imperforate, so that the 

 body cavities of the several polypes are completely separated from one 

 another, and in this respect our observations accord vpith those of 

 KoUiker on Pminatula, though in the allied genus Pteroeides he has 

 shown that wide apertures exist in the septa, thus placing the polypes 

 in direct communication with one another 



The bottom of the polype cavity is separated from the dorsal or 

 lateral canal of the rachis by a very thin wall (Figs. 3 and 4), and the 

 cavities of the ventral polypes appear to communicate with the 

 meshes of the spongy connective-tissue of the rachis-wall. 



The free oral ends of the polypes have thicker walls than the parts 

 which ai-e fused to form the leaf ; and these free ends are strengthened 

 by numerous very large and stout spicules, whose direction is 

 mainly longitudinal. 



The longitudinal muscles of the rachis are not prolonged into the 

 leaves, the muscular system of which is extremely feebly developed. 



b. The Calyx. — As in i^!/?»'c?i//Hr(, the calyx (Figs. 3 and 4 g h,) is 

 produced into eight hollow processes, alternating with the tentacles. 

 These processes are longer and more pointed than in Funlculina, and 

 are stiffened by very numerous spicules, many of which are of very 

 large size ; indeed the spicules are both more abundant and of greater 

 size in the calyx than in any other part of the polype. In most of the 

 polypes the ends of the spicules project freely beyond the ends of the 

 processes for a short distance ; but this condition is almost certainly 

 to be ascribed to the action of the spirit in which the specimens are 

 preserved having caused the fleshy body substance to contract and so 

 leave the ends of the spicules bare. 



When the polypes are retracted, the calyx processes are by the 

 action of the retractor muscles (Fig. 6 j)) pulled in towards one another, 

 and meeting in the middle form a pointed conical cover completely 

 protecting the entrance to the polype cavity (Fig. 3.) 



The calcareous spicules, which form so characteristic an element 

 in the structure of I'ennatula, may be described here. They occur in 

 great numbers along the whole length of both upper and under surfaces 

 of the leaves, being more closely placed along the lines of division 

 between the component polypes (Fig. 5) than at the intervening 

 portions. In the free oral ends of the polypes, and especially in the 

 calices, they are far more numerous than in other parts of the polypes, 

 being set so close together as to be almost in contact with one another. 



They are also, as we have seen, exceedingly abundant in the dermis 

 of both stalk and rachis. 



The spicules, which are always mesodermal structures, vary much 

 in size in different places. They are straight rods, about twenty times 

 as long as they are wide. In the polypes the smallest spicules have a 

 length of about O-OOoin., while the largest ones measure 0-046in. long 

 by 0-002in. wide, the average length being about 0-Oloin. The 



