PENNATULA. 



131 



The Pennatula, (Fig. 71,) has been termed the sea pen, 



from tlie circumstance of its calcare- 

 ous axis, or stem, having a double 

 set of branches, extending in the 

 same plane from both the sides, like 

 the vane of a quill, and of its series 

 of polypes being set along one edge 

 of each branch, like the filaments 

 which arise from the fibres of the 

 feather. Some of these polypes are 

 seen magnified in Fig. 72. Immense 

 numbers of these curious animals are 

 met with in different parts of the ocean. If they possessed 

 in any degree the power of locomotion, which many natura- 

 lists have ascribed to them, we should be able to ascertain 

 wdiether all their movements are conducted by a common 

 volition, or whether they are performed independently of 

 one another. It has often, indeed, been asserted, that pen- 

 natulse swim through the water by their own spontaneous 

 movements, consisting either in the waving up and down of 

 the lateral branches, or in the simultaneous impulses of the 

 tentacula of all the polypes. Cuvier even represents the 

 polypes of the pennatula as having the power of keeping 

 time, while they are waving the mass through the water, as 

 if they were all actuated by a single undivided volition. 

 But Dr. Grant, who has watched the motions of these ani- 

 mals with great care, is led by his observations to the con- 

 clusion that pennatulae are not in reality possessed of an}'- 

 such locomotive faculty; but that they are carried to and fro 

 in the ocean, like the gulf weed, without the slightest vo- 

 luntary power of directing their course. Whatever may be 

 the result of the combined movements of the tentacula, the 

 arms are certainly incapable of those inflections which have 

 been supposed to supply the means of progressiv^e motion. 



It is only when the contractile flesh of the polypus is re- 

 leased from the restraint which the solid axis imposes upon 

 its movements, that the animal becomes capable of any dis- 

 tinct power of locomotion. Such is the condition of the 



