00 THE DAWN OF LIFE. 



tions of the process, the new segments were to detach them- 

 selves. 



" 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. priori reason why 

 a Foraminiferal organism should not attain the same dimen- 

 sions as a Poriferal one, — the intimate relationship of the two 

 groups, notwithstanding the difference between their skele- 

 tons, being unquestionable. 



" 2. The difficulty arising from the zoophytic plan of growth 

 of Eozoon is at once disposed of by the fact that we have in 

 the recent Polytrema (as I have shown, o^:>. cit, p. 235) an 

 organism nearly allied in all essential points of structure 

 to Rotalia, yet no less aberrant in its plan of growth, having 

 been ranked by Lamarck among the Millepores. And it 

 appears to me that Eozoon takes its place quite as naturally in 

 the Nummuline series as Polytrema in the Potaline. As we 

 are led from the typical B/Otalia, through the less regular 

 Planorbulina, to Tinoporus, in which the chambers are piled 

 up vertically, as well as multiplied horizontally, and thence 

 pass by an easy gradation to Polytrema, in which all regularity 

 of external form is lost ; so may we pass from tbe typical 

 Operculina or Nummulina, through Heterostegina and Cyclo- 

 clypeus to Orbitoides, in which, as in Tinoporus, the chambers 

 multiply both by horizontal and by vertical gemmation ; and 

 from Orbitoides to Eozoon the transition is scarcely more 

 abrupt than from Tinoporus to Polytrema. 



" The general acceptance, by the most competent judges, of 

 my views respecting the primary value of the characters fur- 

 nished by the intimate structure of the shell, and the very 

 subordinate value of plan of growth, in the determination of 

 the affinities of Foraminifera, renders it unnecessary that I 

 should dwell further on my reasons for unhesitatingly affirm- 

 ing the Nummuline affinities of Eozoon from the microscopic 

 appearances presented by the proper wall of its chambers, 

 notwithstanding its very abberant peculiarities ; and I cannot 

 but feel it to be a feature of peculiar interest in geological 

 inquiry, that the true relations of by far the earliest fossil yet 



