150 



DR A. MILNES MARSHALL ON THE 



for thinking, from the small size and somewhat stunted appearance of the deep 

 water specimens, that the species is typically a shallow water one, and it is very 

 possible that the increase in development of spicules is due directly to the 

 change of environment. 



All the specimens of Kophobelemnon and also those of Pennatula obtained 

 below 500 fathoms contain large quantities of sand mixed with Foraminifera 

 shells, both in the polyp cavities and in the tentacular cavities, and also 

 encrusting the exterior. The specimens of Umbellularia, Diibenia, and Virgu- 

 laria brought up at the same time are, however, perfectly clean and free from 

 sand. Whether this indicates difference in habits or is merely accidental, I 

 have no means of ascertaining ; the specimens of Pennatula from shallow 

 water have no sand in the polyp cavities, or but very little. 



Morphology. — The chief points of morphological interest on which light is 

 thrown by the " Triton " specimens appear to concern the structure of the 

 zooids of Pennatula and Unibellula ; and the relations of the plane of symmetry 

 of the polyps established in Pennatula, Kophobelemnon, and Unibellula. 



DESCRIPTION OF THE FIGURES ON PLATES XXL— XXV. 



All the figures were drawn with the camera. -Figures 8, 28, and 33 are not taken from 

 single sections, but are constructed from a number of separate camera drawings of the several 

 parts shown. The numbers beneath the figures indicate in diameters the magnifying power 

 employed in each case. 



Alphabetical List 



a, rachis. 



b, stalk. 



c, stem. 



d, polyp. 



dc, main dorsal canal of rachis. 

 dl, leaf. 



e, zooid. 

 /, large zooid. 

 y, body cavity of polyp. 

 h, body cavity of zooid. 

 i, spicule. 

 h, spicular plate. 

 I, calyx process. 

 /', cavity of calyx process. 

 Ic, main lateral canal of rachis. 

 Im, longitudinal muscles of rachis and stalk. 

 m, mescutery or septum. 



of References. 



n, mouth. 



o, ovum. 



o, germinal cell or primitive ovum. 



p, long mesenterial filament. 



r, cilia of siphonoglyphe. 



rm, retractor muscle of polyp. 



s, stomodajum. 



t, tentacle. 



t', cavity of tentacle. 



u, pinnule of tentacle. 



v, spermatosphere. 



vc, main ventral canal of rachis. 



w, ectoderm. 



x, mesoderm. 



x', nutrient canals of m esoderm. 



y, end o derm. 



