VOL. XLVIII.] PHILOSOPHICAL TRANSACTIONS. 543 



racter of which being exactly the same with the nautili, Mr. B. makes no scruple 

 to class them together. 



Whoever will examine nicely bodies of any genera, will have a difficulty to 

 say, where they begin, and where they end ; the gradation is so insensible that 

 they must be bewildered. From the orthoceratitfe, which is doubtless a species 

 of nautilus, we gradually proceed to the belemnites. The orthoceratites is 

 a straight concamerated shell, ending in a point ; some of which are seen 

 in stone 18 inches long. See fig. 6, 7, 8, Q, and l6. The nucleus, or al- 

 veolus of the belemnites, is likewise a straight concamerated shell or body, 

 exactly resembling the other in shape and structure, but of a smaller species, 

 fig. 10 and 14 ; and, from the very great analogy, may reasonably be deemed to 

 be of the same family. In the conic cavity of the belemnites, fig. 1 1 , that con- 

 tains the nucleus, it is very common to observe visible marks of a shelly sub- 

 stance, as a further confirmation that the nucleus was a testaceous body. 



And now a word as to the belemnites itself, the counter part to the other. 

 It has indeed been truly matter of speculation, how that huge solid substance 

 called the belemnites, exclusive of the nucleus, could be formed ; and how it 

 happens that some should have the nucleus within them, others not ; the cavity 

 to contain the same in some very small, in others scarcely or not at all visible. 



These are the main difliculties, all which Mr. B. endeavours to elucidate; but 

 first acknowledges his obligation to Mons. de Peysoimel, and particularly to Mr. 

 John Ellis, f.r.s. for their curious observations on the nature of coral, on which 

 this latter part of Mr. B.'s hypothesis is founded. They have plainly demon- 

 strated, that many bodies which we always took to be vegetable from their ap- 

 pearance, are really animal, and constructed by the polype ; and that several co- 

 ralline substances, hitherto reputed marine plants, are thick beset with a prodi- 

 gious quantity of seedling-shells, too small for the naked eye to see, close by 

 each other, as diamonds in a bodkin, ready to come forth in due time out of their 

 several nests or cellules ; see Phil. Trans, vol. xlvii, p. 445, and vol. xlviii. p. 

 115. Hence he submits, if it is not highly probable that the testaceous tribe in 

 general are generated like butterflies, and flies of all kinds, the one from a mag- 

 got, the other from a polype } Nay, it appears presumptive, that it must be so 

 with a great many. On which circumstance he proceeds, that as corals in ge- 

 neral, from late observation, seem to be constructed by polypi, what inconsistency 

 then to believe them to be the primary state of all or most of the testaceous 

 tribe? If so, it is almost beyond a conjecture, that the body called a bclenmites 

 (which, on being put into acids, is found to ferment in like manner as coral, 

 and other cretaceous bodies), is formed likewise by a polype, I'rom which tlie 

 nucleus seems to be the ultimate state. 



