PLITMATELLA REPENS. 159 



in, and the latter letting it out. The mouth of 

 the bag is, so to speak, tied round the creature's 

 neck just below the tentacles, which are the only 

 portions of it that are left free. Tlie investing 

 sack has in nearly every case the power of secreting 

 an external sheath, more or less solid, and which 

 branches forming numerous cells, in which the mem- 

 bers of the family live in a socialistic community, 

 having, as it were, two lives, one individual, and 

 the other shared in common with the rest. 



The whole group of tubes and cells, Avhatever 

 may be the form in which they are aggregated, is 

 called the Polypai^y^ or, as Dr. All man prefers, the 

 CcenoBcium^ (hollow house;) the creature he names 

 a Polypide^ (polyp-like;) and the disk which bears 

 the tentacles Lophophore^ (crest-bearer.) There 

 are some more hard words to be learnt before the 

 student can enjoy himself scientifically among the 

 Polyzoa, and we shall be compelled to employ some 

 of them before we have done; but will now endeavour 

 to describe what was presented to our view by the 

 specimen obtained from the Hampstead Fond. 



The general aspect of a branch of Plumatella 

 repens — the creature we have to describe — is given 

 in the drawing annexed. When all was quiet, the 

 mouths of the basfs belono^ini? to each cell were 

 slowly everted, and out came a numerous bundle 

 of tentacles, which were either spread like the corolla 



