7. Anthozoa (incl. Hydrocorallia). B. Alcyonaria. 55 



comes insensitive (first towards the base) and then bends over, having lost its 

 geotropic sensitiveness. In order to regain sensitiveness the organism must 

 pass through all the phases above described. 



Kiikenthal( 3 ) placed specimens of Alcyonium, Pteroeides and Ewnicella in 

 water which had been rendered poor in oxygen by previous heating. The 

 colonies dilated, the increased intake of water serving to carry in a larger supply 

 of oxygen. From the pores on the upper part of the stem of Pter. water is for- 

 cibly expelled on stimulation of the organism. 



Musgrave states that Pennatula, Pteroeides, Virgularia and Anthoptilum agree 

 in having 4 large central canals. The 2 lateral ones are shorter, the dorsal 

 extends quite, the ventral nearly to the end of the stalk. The dorsal and 

 ventral canals communicate by numerous apertures or canals in the vertical 

 septum which divides them ; the lateral canals communicate with the other two, 

 and the crelentera of all the zooids communicate with the 4 central canals. In 

 the stalk the large canals are connected by many apertures with the spongy 

 tissue of the internal body wall. Particles of carmine suspended in the water 

 in which Penn. rubra and phosphorea were living for 4 days were found free 

 in the auto- and siphonozooids and ingested in the mesenterial filaments of the 

 former, free in the canals connecting the coelentera with the central canals, 

 and in these latter, and ingested in the cells lining the coelentera and the large 

 canals. There is, therefore, a very complete system of communication between 

 all parts of the colony, and the lining of the crelentera and large canals is 

 nutritive. The fluid in the canals is viscid, due to the mucoid secretion of the 

 gland cells in their lining. Injection experiments show that in P. p. the dorsal 

 and ventral canals open to the exterior at the extreme end of the stalk near 

 which are 6 (4 in r.) other pores, and there are 4 pores in the median dorsal 

 naked streak of the rachis. Similar experiments on Pteroeides show that the 

 dorsal canal has an external opening at the end of the stalk near which are 

 several other pores, there are also 4 dorsal pores near the apex of the racbis. 

 The aperture of the ventral canal is inhalant under certain conditions. The 

 body wall of the stalk contains an outer layer of longitudinal and an inner 

 layer of transverse (and some circular) muscles, the latter are concerned in 

 maintaining, by peristaltic action, dilatation and contraction of the stalk and 

 rachis, thus controlling the quantity of fluid in the canals. Near the tip of 

 the stalk the muscular tissue largely gives place to spongy tissue--a deeply- 

 staining matrix traversed in all directions by canals, lined with epithelium, 

 opening into the dorsal and ventral canals, and also to the exterior by a de- 

 finite number of pores at the tip of the stalk. This tissue becomes turgid by 

 its canals becoming filled with liquid. In large Anth. there is a ring-like zone 

 on the upper portion of the stalk caused by an extraordinary growth of spongy 

 tissue, just below this the stalk is studded with small siphonozooids the cavities 

 of which communicate, through the canals of the spongy tissue, with the central 

 canals. This thickened zone is probably capable of great dilatation and the 

 presence of muscles on its inner surface shows that it is a pumping apparatus, 

 probably to drive fluid upwards into the rachis. In Pter. there is, in the 

 upper portion of the stalk, a powerful internal transverse sphincter. The main 

 impetus of the circulation arises in the stalk. Deep-sea Pennatulids seem 

 to possess certain powers of locomotion ; the author points out how the muscu- 

 lature would render this possible. 



