156 PHILOSOPHICAL TRANSACTIONS. | ANNO 1751. 



the same shape and colour ; so that the substance of coral agrees with its bark 

 in the primitive arid constituent parts, which seem to be the same in both. 



In pieces of coral broken transversely, are often observed some prominent 

 wrinkles, which disengaging themselves from the exterior wrinkles above-men- 

 tioned, run towards the centre (fig. 1, u.) Hence it plainly appears, that there 

 is an affinity or connection between the interior and exterior wrinkles. To the 

 exterior wrinkles, and to the whole outer surface of the hard part of the coral 

 (fig. 2, a, s, e, s,) there is closely attached a white or pale pellicle (fig. 1, g, fig. 

 5, n, n,) which is pretty soft, and composed of vascular and follicular minute 

 membranes, which, by their interlacing, form a reticular body. The whole is 

 accompanied with small vessels, which contain a whitish juice, diffused through 

 all the folliculi or membranulae ; which have also attached to them certain 

 very small red corpuscles, united together by means of other membranulae. 



These corpuscles are nearly of a spherical figure, and in size and shape ex- 

 actly like those of the ashes of the coralline substance, and of the bark : so that 

 we may properly say, that these little bodies constantly remain entire, even after 

 the action of the fire ; having undergone no other change but in their 

 colour. In this pellicle (fig. 5, n, u,) the globular corpuscles are not numerous, 

 but the greatest part of the said pellicle is occupied by very white membranes, 

 from which it takes its colour, and not from the red globular corpuscles. This 

 pellicle, lying immediately on the coral, deposits the red corpuscules, and adapts 

 them to it : and thence it is that the wrinkles are covered as it were, by ex- 

 tremely small hemispheres ; and these infallibly show the formation of the coral- 

 line substance. If any one should ask, whence can these little spheres derive 

 their origin ? Dr. D.'s answer would be, without hesitation, from the polypi of the 

 coral. And the reason is, that if these polypi produce their eggs, as will be shown 

 in the sequel, covered with such corpuscules, we may justly infer that cor 

 puscles of the same nature, wherever they are found, are formed by the same 

 polypi. 



To this white pellicle is attached the bark of the coral (fig. 2, t, t, e, s, s,) 

 which is soft, of a vermillion colour, or of a brighter colour than the coralline 

 substance. It is formed of very fine membranulae, or net-work ; to which are 

 annexed, and reciprocally fastened, the red globular corpuscles, which cause its 

 deeper colour. It is along this bark, that cylindrical vessels (fig. 2, t, t, t, t, 

 fig. 5, i, fig. 6, n,) are observed to run lengthways of the coral ; which appear 

 by the microscope to be parallel to each other, and out of which issue laterally 

 other vessels infinitely small, (fig. 5, t, t, t,) which have a communication with 

 the above-mentioned membranulae. The use of these vessels is to give nutri- 

 ment to the coral, by means of a milky juice contained in them. The surface of 

 this bark is slippery and uneven, when the coral has been just fished out of 



