86 THE DAWN OF LIFE. 



surface. Such, at least, are the only interpretations I can put 

 upon the appearances presented by decalcified specimens. 

 For on the one hand, it is frequently to be observed that two 

 bands of serpentine (or other infiltrated mineral), which repre- 

 sent two layers of the original sarcode-body of the animal, 

 approximate to each other in some part of their course, and 

 come into complete continuity; so that the upper layer would 

 seem at that part to have had its origin in the lower. Again, 

 even where these bands are most widely separated, we find 

 that they are commonly held together by vertical lamellee of 

 the same material, sometimes forming mere tongues, but often 

 running to a considerable length. That these lamellae have 

 not been formed by mineral infiltration into accidental fissures 

 in the shell, but represent corresponding extensions of the 

 sarcode-body, seems to me to be indicated not merely by the 

 characters of their surface, but also by the fact that portions 

 of the canal-system may be occasionally traced into con- 

 nection with them. 



"Although Dr. Dawson has noticed that some parts of the 

 sections which he examined present the fine tubulation charac- 

 teristic of the shells of the jSTummuliue Foraminifera, he does 

 not seem to have recognised the fact, which the sections 

 placed in my hands have enabled me most satisfactorily to 

 determine, — that the proper walls of the chambers every- 

 where present the fine tubulation of the ISTummuline shell ; a 

 point of the highest importance in the determination of the 

 aflSnities of Eozoon. This tubulation, although not seen with 

 the clearness with which it is to be discerned in recent exam- 

 ples of the Nummuline type, is here far better displayed than 

 it is in the majority of fossil Nummulites, in which the tubuli 

 have been filled up by the infiltration of calcareous matter, 

 rendering the shell-substance nearly homogeneous. In Eozoon 

 these tubuli have been filled up by the infiltration of a mineral 

 different from that of which the shell is composed, and there- 

 fore not coalescing with it; and the tubular structure is con- 

 sequently much more satisfactorily distinguishable. In de- 

 calcified specimens, the free margins of the casts of the 

 chambers are often seen to be bordered with a delicate white 



