118 THE CANADIAN NATURALIST. [April 



the structure of that stony Alga, with which that of Eozoon has 

 nothing whatever in common. 



The objections which not unnaturally occur to those familiar 

 with only the ordinary forms of Foraminifera, as to the admission 

 of Eozoon into the series, do not appear to me of any force. These 

 have reference in the first place to the great size of the organism; 

 and in the second, to its exceptional mode of growth. 



1. It must be borne in mind that all the Foraminifera normally 

 increase by the continuous gemmation of new segments from those 

 previously formed; and that we have ; in the existing types, the 

 greatest diversities in the extent to which this gemmation may 

 proceed. Thus in the Globigerina^ whose shells cover to an un- 

 known thickness the sea-bottom of all that portion of the Atlantic 

 Ocean which is traversed by the Gulf-stream, only eight or ten seg- 

 ments are ordinarily produced by continuous gemmation ; and if 

 new segments are developed from the last of these, they detach them- 

 selves so as to lay the foundation of independent Globigerince. On 

 the other hand in Cydochjpeus, which is a discoidal structure attain- 

 ing two and a quarter inches in diameter, the number of segments 

 formed by continuous gemmation must be many thousand. Again, 

 the ReceptacuUhs 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 gemmation (after the manner of Tlnoporus or Orbitoi- 

 des) 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 ac- 

 count 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 

 same category. The very same continuous gemmation which has 

 produced an Eozoon would produce an equal mass of independent 

 Globigerince, if after eight or ten repetitions of the process, the 

 new segments were to detach themselves. 



It is to be remembered, moreover, that the largest masses of 

 sponges are formed by continuous gemmation from an original 

 Rhizopod segment ; and that there is no a j^'iori reason why a 

 Foraminiferal organism should not attain the same dimensions as 

 a Poriferal one, — the intimate relationship of the two groups, not- 

 withstanding the difference between their skeletons, being unques- 

 tionable. 



* First Decade of Canadian Fossils, pi. x. 



