TUBULIPORA. 205 



f 



and set horizontally, so that their apertures project on 

 the margin. 



And here is another form still. A narrow band of 

 shelly matter, not much thicker than a pin, creeps 

 along the root of the weed, and then divides into two 

 spreading branches. The tubes are arranged here in 

 transverse rows along the whole surface, in such a 

 manner that a central line divides them into two sets, 

 those on either hand arching outwards towards that 

 side, so that a furrow separates them. 



All these pretty objects and they are very attrac- 

 tive to the eye when magnified are closely allied to 

 each other ; they are different species of the genus 

 Tululipora. At least, they are the " mortal remains" 

 of such animals, for they are at present mere skeletons: 

 the animals, as I have already observed, have died 

 out. They are exceedingly delicate, and a very short 

 exposure to the air is enough to close their frail lease 

 of life ; so that it is rather rare even for the experi- 

 enced naturalist, who is conversant with such crea- 

 tures, to get a glimpse of them in healthy vitality. 



Each of these tiny tubes is inhabited, during life, 

 by a creature of transparent tissues, whose structure 

 manifests a relationship, not very remote, to the ten- 

 ants of bivalve shells, such as the oyster or mussel. 

 The tube represents the two valves of the shell , united 

 along the edge, and open at one end ; but this asser- 

 tion must not be considered as anything more than 

 an aid to your conceptions of the affinity of the two 

 forms; for considerable modifications would require 



