74 PRINCIPLES OF PALEONTOLOGY. 



filled to its minutest internal recesses with the substance of the 

 living animal, and covered externally with a layer of the same 

 substance, giving off a network of interlacing filaments. 



Such, in brief, is the structure of the living Foraminifera ; 

 and it is believed that in Eozoon we have an extinct example 

 of the same group, not only of special interest from its imme- 

 morial antiquity, but hardly less striking from its gigantic 

 dimensions. In its original condition, the entire chamber- 

 system of Eozoon is believed to have been filled with soft 

 structureless living matter, which passed from chamber to 

 chamber through the wide apertures connecting these cavities, 

 and from tier to tier by means of the tubuli in the shell-wall and 

 the branching canals in the intermediate skeleton. Through 

 the perforated shell-wall covering the outer surface the soft 

 body-substance flowed out, forming a gelatinous investment, 

 from every point of which radiated an interlacing net of deli- 

 cate filaments, providing nourishment for the entire colony. 

 In its present state, as before said, all the cavities originally 

 occupied by the body-substance have been filled with some 

 mineral substance, generally with one of the silicates of mag- 

 nesia; and it has been asserted that this fact militates strongly 

 against the organic nature of Eozoon, if not absolutely dis- 

 proving it. As a matter of fact, however as previously no- 

 ticed it is by no means very uncommon at the present day 

 to find the shells of living species of Foraminifera in which 

 all the cavities primitively occupied by the body-substance, 

 down to the minutest pores and canals, have been similarly 

 injected by some analogous silicate, such as glauconite. 



Those, then, whose opinions on such a subject deservedly 

 carry the greatest weight, are decisively of opinion that we are 

 presented in the Eozoon of the Laurentian Rocks of Canada 

 with an ancient, colossal, and in some respects abnormal type 

 of the Foraminifera. In the words of Dr Carpenter, it is not 

 pretended that " the doctrine of the Foraminiferal nature of 

 Eozoon can be proved in the demonstrative sense ; " but it 

 may be affirmed " that the convergence of a number of separate 

 and independent probabilities, all accordant with that hypothesis, 

 while a separate explanation must be invented for each of 

 them on any other hypothesis, gives it that high probability 

 on which we rest in the ordinary affairs of life, in the verdicts 

 of juries, and in the interpretation of geological phenomena 

 generally." 



It only remains to be added, that whilst Eozoon is by far 

 the most important organic body hitherto found in the Lauren- 

 tian, and has been here treated at proportionate length, other 



