548 On the Structure and Affinities of Eozoon Canadense. [Dec. 15^ 



is a character of primary importance in this group, the plan of growth and 



the mode of coramunication of the chamhers being of secondary value, and 

 the disposition of the "intermediate skeleton" and its "canal-system" 

 being of yet lower account. 



I cannot refrain from stopping to draw your attention to the fact, that 

 the organic structure and the zoological affinities of this body, which was 

 at first supposed to be a product of purely physical operations, are thus 

 determinable by the microscopic examination of an area no larger than a 

 pin-hole — and that we are thus enabled to predicate the nature of the 

 living action by which it was produced, at a geological epoch whose 

 remoteness in time carries us even beyond the range of the imagination, 

 with no less certainty than the astronomer can now, by the aid of " spectrum 

 analysis," determine the chemical and physical constitution of bodies whose 

 remoteness in space alike transcends our power to conceive. 



The only objections which are likely to be raised by palaeontologists to 

 such a determination of the nature of Eozoon, would be suggested by its 

 zoophytic mode of growth, and by its gigantic size. The first objection, 

 however, is readily disposed of, since I have elsewhere shown * that a 

 minute organism long ranked as zoophytic, and described by Lamarck 

 under the designation Millepora rubra, is really but an aberrant form of 

 the Rotaline family of Foraminifera, its peculiarity consisting only in 

 the mode of increase of its body, every segment of which has the charac- 

 teristic structure of the Rotalince ; and thus, so far from presenting a 

 difficulty, the zoophytic character of Eozoon leads us to assign it a place in 

 the Nummuline series exactly corresponding to that of Polytrema in the 

 Rotaline. And the objection arising from the size and massiveness of 

 Eozoon loses all its force when we bear in mind that the increase of Fora- 

 minifera generally takes place by gemmation, and that the size which 

 any individual may attain mainly depends (as in the Vegetable kingdom) 

 upon the number of segments which bud continuously from the original 

 stock, instead of detaching themselves to form independent organisms ; so 

 that there is no essential difference save that of continuity, between the 

 largest mass of Eozoon and an equal mass maJe up of a multitude of 

 Nummidites. Moreover there is other evidence that very early in the 

 Palaeozoic age the Foraminiferous type attained a development to which we 

 have nothing comparable at any later epoch ; for it has been shown by 

 Mr. J. W. Salter t that the structure of the supposed coral of the Silu- 

 rian series to which the name Receptaculites has been given, so closely 

 corresponds with that which I have demonstrated in certain forms of the 

 Orbitolite type;];, as to leave no doubt of their intimate relationship, 

 although the disks of Receptaculites sometimes attain a diameter of 1 2 

 inches, whilst that of the largest Orbitolite I have seen does not reach 



* Introduction to the Study of the Foraminifei-a, p. 235. 



t Can:^dian Organic Eemains. Decade i, % Phil. Trans. 1855. 



