33 



fibre. But none of such conditions has been ever found. It follows 

 that a substance differing from either formerly filled these minute 

 perforations, a substance little if at all less durable than the 

 skeleton fibre, far more durable than the mere soft intermediate 

 substance. Such a substance precisely answers to the terms 

 under which a true epidermis is properly described, which is not 

 fibrous in texture but pretty nearly homogeneous, and so strong 

 as to have been described by a well-known modern author as 

 " resisting suppuration, maceration, and other modes of destruc- 

 tion, for a great length of time*." 



I have already stated that I had previously satisfied myself of 

 the existence of a distinct polyp-skin or epidermis. A peculiar 

 appearance of corrugation, very difficult to describe but always 

 present in good casts, and with a vacant space between it and the 

 actual fossil, left this beyond a doubt, though at that time no spe- 

 cimen had been found showing the remains of the epidermis 

 itself preserved on the actual fossil. In specimens since found 

 with remains of epidermis preserved, there is, of course, no such 

 vacant space. Attached to this epidermis and of a similar nature, 

 and at least as durablef as itself, there evidently existed during 

 the life of the animal hair-like processes scattered over a large 

 part of its surface. 



Plate VIII. figs. 4 and 5 show examples of the appearances of 

 casts of two very different species of Ventriculidse, in each of which 

 these perforations are present. It will be seen that a different 

 arrangement of them exists in the two cases. 



It would be only tedious to the reader to carry him through 

 the whole process of induction, by which, not through any hasty 

 conclusion, but as the result of careful and very cautious inves- 

 tigation, the reality seemed to force itself upon me that the 

 sources of these perforations corresponded to those curious move- 

 able processes which exist on the surface of some few of the 

 higher zoophytes, and which have been well described by Prof. 

 ReidJ. The determination may seem obvious enough on its an- 



* Elliotson's ' Physiology,' 5th ed. p. 270 ; and see Todd and Bowman's 

 ' Anatomy and Physiology, 5 vol. i. p. 414. The appearance of the polyp- 

 skin, as preserved by the deposit in it of sulphuret of iron, and examined 

 under the microscope, has been recognized by some of my friends wholly 

 unfamiliar with these or other fossils as bearing a striking resemblance to 

 the human epidermis examined in the same way. 



f I have found by actual experiment that, at least in some species, the 

 hair-like processes of recent polypifers are, though hollow, less easily de- 

 structible by maceration in llq. potassce than are the other parts of the epi- 

 dermis. And I cannot avoid noticing here, that on such maceration a gra- 

 nular appearance was assumed very similar to that of the Ventriculidse. It 

 is unnecessary to dwell on this effect of the potash contained in the same 

 felspar rocks to whose disintegration the siliceous fluid has been ascribed. 



I Ann. and Mag. Nat. Hist. vol. xvi. p. 385, &c. 



C 



