WHAT IS EOZOON ? 89 



the suggestion that it may have been of kin to NuUipore, I 

 can offer the most distinct negative reply, having many years 

 ago carefully studied the structure of that stony Alga, with 



rhich that of Eozoon has nothing whatever in common. 

 ' The objections which not unnaturally occur to those familiar 



ith only the ordinary forms of Foraminifera, as to the admis- 



lon of Eozoon into the series, do not appear to me of any 

 rce. These have reference in the first place to the great size 

 the organism ; and in the second, to its exceptional mode of 



rowth. 



" 1. It must be borne in mind that all the Foraminifera nor- 



lally increase by the continuous gemmation of new segments 

 )m those previously formed; and that we have, in the 



cisting types, the greatest diversities in the extent to which 



lis gemmation may proceed. Thus in the Globigerinae, 

 whose shells cover to an unknown thickness the sea bottom of 

 all that portion of the Atlantic Ocean which is traversed by 

 the Gulf Stream, only eight or ten segments are ordinarily 

 produced by continuous gemmation ; and if new segments are 

 developed from the last of these, they detach themselves so as 

 to lay the foundation qf independent Globigerinae. On the 

 other hand in Cycloclypeus, which is a discoidal structure 

 attaining two and a quarter inches in diameter, the number of 

 segments formed by continuous gemmation must be many 

 thousand. Again, the Keceptaculites of the Canadian Silurian 

 rocks, shown by Mr. Salter's drawings* to be a gigantic 

 Orbitolite, attains a diameter of twelve inches ; and if this 

 were to increase by vertical as well as by horizontal gemma- 

 tion (after the manner of Tinoporus or Orbitoides) so that one 

 discoidal layer would be piled on another, it would form a 

 mass equalling Eozoon in its ordinary dimensions. To say, 

 therefore, that Eozoon cannot belong to the Foraminifera on 

 account of its gigantic size, is much as if a botanist who had 

 only studied plants and shrubs were to refuse to admit a tree 

 into the sam6 category. Tlie very same continuous gemma- 

 tion which has produced an Eozoon would produce an equal 

 mass of independent Globigerinae, if after eight or ten repeti- 

 * First Decade of Canadian Fossils, pi. x. 



