728 PHILOSOPHICAL TEANSACTIONS. [aNNO 1776. 



I come now to the outside covering or skin of the animal. As few have been 

 at the pains to examine the surface of the gorgonia accurately, it has scarcely 

 yet been noticed, that they are clothed with a kind of scales, and some of them 

 so remarkably covered, and the scales so well adapted to the particular parts, that 

 one might reasonably be induced to think, that nature has given them this de- 

 fence, as she has done in like manner to the several parts of snakes and lizards, 

 as a kind of armour to protect them from external injuries. As instances of the 

 above, I shall only mention, that the surface of the stem, as well as the mouth 

 of the cells of the gorgonia placomus, are defended by long pointed scales ; see 

 Essay on Corallines, p. 27, t. a, I to 3 ; and the gorgonia verticillata (of which 

 an elegant specimen is to be seen in the British Museum) has also very remark- 

 able scales of different sizes round the mouths and on the skin ; see Essay of 

 Corallines, t. 26, f. s, t. The gorgonia lepadifera has a most remarkable 

 variety, placed like tiles, one over another, for the defence of the mouth of the 

 cells that inclose the polype suckers ; besides, there is a small kind of scales, 

 that covers the surface of the stem and branches ; see fig. 12. 



From the skin we are naturally led to speak of the flesh of the gorgonia, or 

 what the modern naturalists call the bark or cortex. Whoever has examined the 

 flesh of the gorgonia, well preserved at the sea-side in spirits, will find, on dis- 

 secting them, proper muscles and tendons for extending the openings of their 

 cells ; for sending forth from thence their polype suckers in search of food ; for 

 drawing them in suddenly, and contracting the sphincter muscles of these starry 

 cells, in order to secure these tender parts from danger ; and also that there is, as 

 we have already mentioned, proper secretory ducts, to furnish and deposit the 

 osseous matter, for the supply of the bone, both of the stem and branches as 

 well as the base, to secure its station with firmness, amidst the boisterous ele- 



construction of timber, that the cell-Uke divisions in the branch of a walnut tree are onl)- a row of 

 single blebs of pitli. But the microscope discovers to us, on viewing one of tliese cross membranes, 

 that it is composed of many cells shrunk up and united together ; for, on viewing the flat surface of 

 one of them, it appeared full of circles intersecting each other, like a thick transverse section of 

 many other dried piths pressed together : besides, the thicker part of this shrunk-up walnut pith, all 

 round next the inside close to the wood, when magnified, plainly showed the same appearance of 

 blebs as in otlier pith. To confirm this observation. May 23, 1*72, I procured a young green shoot 

 of a walnut tree, growing ft'om a branch of tlie preceding year ; and examining the pith, both in 

 upright and transverse sections of this new shoot, I found that they exactly resembled the pitli of 

 many other trees, but were full of sap : and that the ranges of cells or blebs, tliat occupied one of 

 these spaces, could not be less than 100, perhaps double that number of blebs. Dr. Grew takes no- 

 tice, p. 120 in his Anatomy of Plants, that there are other trees, besides tlie walnut tree, whose pith 

 in the last year's shoot shrinks up and forms such cavities ; and an ingenious friend of mine, now en- 

 gaged in an inquiry into the structure of plants, has shewn me a last year's stem of the brassica sylves- 

 tris, or shrubby cabbage, w hose pith is shnink and divided into a single row of cells, like those of the 

 walnut tree of last year's growth. — Orig. 



