TUBlPORIDiE. 489 



locomotion is doubted by other writers, and the pale blue 

 light is said only to be emitted when under the influence 

 of some degree of irritation. 



Alcyonaria. — Actinozoa, in which each polype is fur- 

 nished with eight primately fringed tentacles. Corallum 

 eclerobasic or spicular. 



Alcyonium digitatum, " Fingered Alcyonium " (Fig. 

 237, No. 2). — The French call it Main de Mer, "sea- 

 hand," the Germans Diebshand, "thief's hand." Some- 

 times they are very small ; but when larger are named by 

 the fishermen Cows -paps, and Dead Metis Hands. The 

 mass, at first repulsive, when placed in sea-water gradually 

 expands into delicately pellucid polypes, with crowns of 

 beautiful tentacula. The cells occupied by the polypes are 

 placed at the terminations of canals which run through 

 the polypidom, and which, by their union with each 

 other, serve to maintain a communication between the in- 

 dividual polypes constituting the mass. The rest of the 

 polypidom is made up of a transparent gelatinous sub- 

 stance, containing calcareous spicula, and pervaded by 

 numerous small fibres, which form a sort of irregular net- 

 work. Alcyonidoe aife always attached to submarine 

 bodies. The species already mentioned is exceedingly 

 common round our coasts ; so much so that, as Dr. John- 

 ston says, " scarce a shell or stone can be dredged from 

 the deep that does not serve as a support to one or more 

 specimens." 



The ova, as Professor Grant remarks, placed under the 

 microscope, and viewed by transmitted light, appear as 

 opaque spheres surrounded by a thin transparent margin, 

 which increase in thickness as the ova begin to grow, 

 and such of the ova as lie in contact unite and grow as 

 one ovum. A rapid current in the water immediately 

 around each ovum, drawing along with it all the loose 

 particles and floating animalcules, is distinctly seen moving 

 with an equal velocity as in other ciliated ova ; and a 

 zone of very minute vibrating cilia is quite perceptible, 

 surrounding the transparent margin of all the ova. 



TuBiPORiDiE. — To this family belongs the handsome 

 Tubipora musica, "Organ-pipe Coral" (fig. 237, No. 10), the 

 polypidom of which is composed of parallel tubes, united by 



