360 PHILOSOPHICAL TKANSACTIONS. [aNNO I765. 



sonel's account of the formation of sponges by little animals, that walk to and 

 fro in the labyrinth of the tubes to construct his extraordinary animal fabric. 



In order to explain how near they approach to the alcyoniums in their internal 

 form and manner of growth, Mr. E. has here given the perpendicular and hori- 

 zontal sections of the conmion officinal sponge; because this is in the power of 

 most gentlemen to examine. And at p. 44 of these Abridgments, he has given the 

 perpendicular and horizontal sections of the alcyonium manus marina, both mag- 

 nified and in the natural size; because specimens of this kind are likewise easily 

 obtained, being found in plenty on rocks and shells near the isle of Sheppey, at 

 the entrance of the river Thames. It is observed that the connected tubes of 

 both arise from the part to which they adhere to the rocks, &c. Hence both 

 kinds branch out and swell into irregular lobes; with this difference, that the 

 surface of the sponge is covered with holes guarded with minute points like little 

 spines; the surface of the alcyonium with starry openings of 8 rays, whence the 

 polype-like suckers are protruded, to find out proper nourishment: and these 

 starry openings in one, and the holes in the other, so far correspond, that in 

 both kinds they are found of different sizes; but this is in proportion to the age 

 of the branching tubes that come to the surface. 



In the sections of the alcyonium may plainly be distinguished the reticulated 

 elastic fibres, that enclose the transparent stiff gelatinous part, as in the sponges; 

 but as this gluey substance is of a firmer texture than what is found in sponges, 

 it requires more pains to separate it from the elastic fibres; however, with a little 

 trouble it may be done sufficiently to evince what he has endeavoured to prove, 

 viz. the great proximity there is between the animal life of sponges and alcyo- 

 niums, and consequently that both are animals. 



Before concluding, he endeavours to remove some doubts, which seem to have 

 istressed the generality of curious persons to account for; the one is, what oc- 

 casions those very large holes that appear here and there irregularly on the sur- 

 face of most sponges? the other is, how came those extraneous bodies, such as 

 small shells, stones, and even parts of fucuses, in the middle of these animal 

 bodies? in answer to the first, on cutting open and examining these bodies while 

 recent in sea water, as before shown, we frequently find a variety of different 

 worms, who bore their way into them, and make their nests and retreats there, 

 or perhaps to live on the gelatinous part of the sponge. This the celebrated 

 Donati confirms, in his History of the Adriatic sea; who endeavouring to find 

 out, like Peyssonel, the animal fabricator of the alcyonium primum Dioscoridis, 

 which approaches very near to the sponges, he met with many irregular cavities 

 in it, and also different kinds of inhabitants ; one of them he has particularly 

 described and figured. Vide Donat. Hist. M. Adriat. p. 58. t. 8. fig. g. But he 



