210 HISTORY OF BRITISH ZOOPHYTES. 



work. "That the motion of the water descends to a good 

 depth I prove from those plants that grow deepest in the 

 sea, because they all generally grow flat, in manner of a fan, 

 and not with branches on all sides, like trees, which is so 

 contrived by the Providence of nature, for that the edges of 

 them do in that posture with most ease cut the water flow- 

 ing to and fro ; and should the flat side be objected to the 

 stream, it would soon be turned edge-wise by the force of 

 it, because in that state it doth least resist the motion of 

 the water; whereas, did the branches of the plants grow 

 round, they would be thrown backward and forward every 

 tide. Nay, not only the herbaceous and woody submarine 

 plants, but also the lithophyta themselves affect this manner 

 of growing, as I have observed in various kinds of coral and 

 pori." (Say.) 



In forming their network, the little creatures are taught 

 to give greater strength to the fabric by a few stronger 

 tubes, that proceed lengthways, and a few that irregularly 

 cross the fan. Ellis, in figuring Venus' s fan, has chosen a 

 specimen which shows the ingenuity of the polypes in re- 

 pairing the damage when one of the main stems had been 

 broken through near the base. As the separation of the 

 parts of the great tube was complete, and the upper part of 



