296 On the Structure and Position of Eozoon Canadense. 



regards the generative process,) which, we possess in respect 

 to the best-known existing representatives of the Foraminiferal 

 group, is that which concerns the early stage of its develop- 

 ment. At present we know Eozoon only in its massive forms ; 

 and we have no clue, save that furnished by analogy, to the 

 mode in which these are built up. In the Rotaline series, 

 which is characterized by the coarse perforation of the shell, we 

 find the original spire of Planorbulina overgrown by chambers 

 piled upon it in an irregular acervuline manner ; in Tinoporus, 

 whose young state closely resembles the early form of Planor- 

 bulina, the chambers, successively superposed on the original 

 spire and its marginal extension, are piled in layers of greater 

 regularity ; while in Polytrema similar rotaline chambers bud 

 forth one from another, in such a manner as to give to the 

 organism the aspect of a minute branching Coral, for which it 

 was long mistaken. Now, in virtue of the fine tubulation of 

 the proper walls of its chambers, Eozoon belongs to the 

 Nummuline series, of which I have shown this structure to be 

 the special characteristic ; and this series presents a remark- 

 able parallelism, as regards variations in mode of growth, 

 to the Rotaline. For we may pass from the typical Operculina 

 or Nummidina, through Heterostegina and Gycloclypeus, to 

 Orbitoides, in which, as in Tinojporus, the chambers multiply 

 both by horizontal and by vertical gemmation ; and between 

 this and Eozoon the difference is not greater as regards plan 

 of growth than between Tinojporus and Polytrema.* 



Notwithstanding the striking contrast which is presented 

 between the massive growths of Eozoon and those microscopic 

 Rotalice, Miliolce, etc., which are the examples of the Foramini- 

 feral type most familiar to collectors on our own shores, there is 

 no more essential difference in plan of structure, than that 

 which exists between the most insignificant flowering plant 

 and the gigantic Wellingtonia or the wide -spreading Banyan. 

 In the one case, as in the other, the difference consists, not so 

 much in the size of the individual parts, as in the extent to 

 which these parts are multiplied by the production of new 

 buds in continuity with the pre-existing fabric. A contrast 

 scarcely less remarkable exists among the Foraminifera of the 

 existing epoch. Thus the shells of the minute Globigerince, 

 which cover to an unknown thickness the sea-bottom of all 

 that portion of the Atlantic Ocean which is traversed by the 

 Gulf stream (the " ooze," of which specimens are brought up 

 by the sounding apparatus, containing not less than 95 per 

 cent, of them), consist of not more than eight or ten chambers, 

 showing that the continuous increase of the individual body by 



* See the descriptions of the Structure of these Generic types in my 

 Introduction to the Study of the Foraminifera. 



