EEPORT ON THE A LC YON ARIA. 263 



polyps are cylindrical, relatively large, and stand upright, or at an obtuse angle upon the 

 axial polyps. 



The stolons, which are closely packed together, and sometimes united to fonn plates, 

 spread themselves over foreign bodies, such as masses of sand, Gorgonid axes, &c. From 

 them there arise axial polyps of the first order, and smaller single polyps, of which some 

 may bear buds. 



The main polyps rise, in a somewhat twisted and bent manner, to a height of 160 mm. 

 From their base to the summit, where the retractile portion of the polyp is met with, 

 they decrease slightly in thickness. At the base the diameter is about 3 mm., near the 

 summit r5 mm. The main pol}i3s bear, in part, tube-like lateral polyps disposed in 

 ascending spirals, in part, long axial polyps of the second order, the latter forming long 

 branches which sometimes overtop the main polyps. These, like the main polyps, bear 

 lateral polyps, but seldom short axial polyps of the third order. 



The lateral polyps are cylindrical, have cylindrical calyces, are 5 mm. in length 

 and 1 to r2 mm. in diameter. The outer walls of all the polyps exhibit eight 

 longitudinal ridges and furrows, those of the axial polyps running their course quite 

 independently of those of the lateral polyps. The axial polyps form long tubes, the 

 inner cylinder of which remains the same from the calyx to the base of the polyp, while 

 the polyp wall becomes gradually thicker downwards. This inner cylinder is the 

 extended digestive cavity of the axial polyps ; on its walls the eight mesenteric folds 

 are continued down to the base of the polyps. These folds form, however, in the 

 deeper portion, but slightly projecting elevations. 



In the wall of the polyp tube one can distinguish the ectoderm as a thin covering, 

 the thick mesoderm, and the endoderm lining the cavity. From the mesoderm a thin 

 structureless layer surrounds the endoderm, and is only thickened at the insertion of each 

 mesenteric fold ; then a dense layer of spicules, disposed in several strata, occurs. The 

 dentations of these spicules are so much interlocked that they can with difficulty be 

 separated, while the spicules are further fastened together by a horny envelope, which is 

 not so sharply defined towards the exterior. The outermost stratum of the mesoderm 

 exhibits loosely packed spicules, with a soft gelatinous connecting substance. On this 

 a network of fine endodcrmal canals is spread, which sometimes unite to form larger 

 longitudinal canals ; from these fine endodermal canals pass through the horny layer 

 into the digestive cavity of the polyp. 



From this canalicular network the lateral polyps and the axial polyps of the second 

 order arise, and their digestive cavities have therefore no direct communication with 

 those of the axial polj-ps. In the lateral polyps the body-wall is thin, and contains no 

 horny substance. The retractile portion of the pol}^ contains spicules in longitudinal 

 bundles, which are to be found even in the tentacles. The spicules are fine, bent 

 rods, with scattered, irregularly distributed, prominent sharp spines. Their length and 



