PENNATULID^E. 213 



that posture with most ease cut the water flowing to and fro ; and 

 should the flat side be objected to the stream, it would soon be turned 

 edgewise by the force of it, because in that site it doth least resist the 

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

 round, they would be thrown backward and forward every tide. Nay, 

 not only the herbaceous and woody submarine plants, but also the litho- 

 phyta themselves affect this manner 'of growing, as I have observed in 

 various kinds of corals." 



In the British family there are also (?. verucosa, G. placomus, 

 G. anceps, G. lepadifera, G. umbraculum, G. nobilis. 



The Isis, sea-shrubs belong to this class ; they are small, but nume- 

 rously scattered in the soft fleshy integument, Isis hippuris, or 

 Horse-tails, so called from its" resemblance to the Equisetse, is the 

 type by which this family is illustrated ; it has a jointed stony stem, 

 which rises into many loose branches. The stem or support of the 

 animal consists of white, cylindrical, stony channelled joints, connected 

 together by black, contracted, horny intermediate ones. The flesh is 

 whitish, plump, and full of minute vessels ; the surface of it is full of 

 the little mouths of the cells, which are disposed in a quincunx order, 

 covering the polyps with eight claws. 



PENNATULIDJ2. 



This family derives its name from penna, a quill, which the animal 

 much resembles ; a spiculum from one is shown at No. 3, fig. 103. Natu- 

 ralists call them Sea-pens ; and had they generally applied such simple 

 appropriate terms to the objects of nature, they would have removed a 

 bar to the study of science, and overcome a repugnance commonly felt 

 on entering the enchanting field of knowledge. 



The polypiferous mass of the Pennatula is fleshy or jelly-like ; and 

 the polyps are always found on the margin of the appendages of the 

 polypidom. The skin is tough and horny, and has numerous calcareous 

 spicula in a parallel position to each other, which Dr. Coldstream is of 

 opinion are solid ; and when connected with the body of the animal, 

 seem to be red ; but a slight degree of heat is sufficient to bleach 

 them : they consist of phosphate and carbonate of lime, making thus 

 a near approach to the bone of vertebrate animals. 



On many parts of the coast, when the fishermen haul in their lines, 

 and more especially if baited with mussels, there are found attached to 

 the bait a number of polyps, which the boatmen call Cocks' -combs, but 

 naturalists, Pennatula phosphorea ; they are from two to four inches 



