ALCYONIDM. 247 



the polypidom is squat, with thick spreading arms covered with 

 lobiliform branches, the tubercular polypidoms of which are columnar 

 and obtuse, the spicula green, and the tentacula of the polyps 

 yellow. 



" On a cursory view," says Dr. Johnston, " the polypidom of the 

 three families embraced appear very dissimilar, and accordingly, by 

 many recent authors, they have been scattered over the class, and 

 placed widely asunder. The affinity between them, however, is 

 generally acknowledged, and had been distinctly perceived by some 

 of the earliest zoophytologists. Thus Bohadsch found so much in 

 common in the typical Pennatula and a species of Akyoniufn, that 

 he has not hesitated to describe them as members of the same genus; 

 and, although the more systematic character of Pallas prevented 

 him from falling into this error, if error it can be called, he did not 

 the less recognise the relationship between the genera or families. 

 Pallas also tells us that his Verretillum cynomoriitrn differs from the 

 Alcyoniutn only in this, that the former is a movable and the latter a 

 fixed polypidom ; and he saw with equal clearness the connection 

 which exists between these genera and the shrub-like Gorgonia. Of 

 the Virgiilaria mirabilis^ he had doubts whether it was not rather a 

 species of Gorgonia^ until he perceived that the stem was attenuated 

 at each end, and free ; and of the Sea-pens generally, Ellis remarks 

 that they are ' a genus of zoophytes not far removed from the 

 Gorgonia^ on account of their polyp mouths, as well as having a bone 

 in the inside and flesh without.' ' On the other hand, the Gorgonia 

 seem,' says Pallas, ' with the exception of their homy skeleton, to be 

 nearly similar in structure to the genus Alcyoniiwi ; but as there are 

 species of Gorgonia which are suberose internally, and almost of a 

 uniform medullary consistence, even this mark of distinction fails to 

 separate the tribes, and we have little left to guide us in arranging 

 these osculent species excepting their external habits.'" 



"With most corallines," says Fredol, "the elementary individual, 

 in spite of the adhesion established among them, possesses a vital 

 energy all its own ; it is in some respects quite independent. They 

 have each its own particular will, which it is difficult to mistake for 

 a common will ; but it is not thus with the Pentiatida. Their 

 association consists of a non-adherent polyp, which moves — 

 obscurely, it is true — but still it moves. To what does this lead ? 

 To this : that the parts which they possess in common, in place ot 

 being homy or calcareous — that is, completely inert — are fleshy, 

 with contractile powers ; that is to say, animated. Consequently, 

 the polyp of the Pennatula are less independent of each other than 



