THE PRESERVATION OF EOZOON. 117 



of the two minerals ; yet they are seen to traverse both the 

 pyroxene and the serpentine without any interruption or 

 change. Some sections exhibit these two minerals filling ad- 

 jacent cells, or even portions of the same cell, a clear line of 

 division being visible between them. In the specimens from 

 Grenville on the other hand, it would seem as if the develop- 

 ment of the Eozoon (considerable masses of which were re- 

 placed by pyroxene) had been interrupted, and that a second 

 growth of the animal, which was replaced by serpentine, had 

 taken place upon the older masses, filling up their inter- 

 stices." 



[Details of chemical composition are then given.] 

 " When examined under the microscope, the loganite which 

 replaces the Eozoon of Burgess shows traces of cleavage- 

 lines, which indicate a crystalline structure. The grains of 

 insoluble matter found in the analysis, chiefly of quartz-sand, 

 are distinctly seen as foreign bodies imbedded in the mass, 

 which is moreover marked by lines apparently due to cracks 

 formed by a shrinking of the silicate, and subsequently filled 

 by a further infiltration of the same material. This arrange- 

 ment resembles on a minute scale that of septaria. Similar 

 appearances are also observed in the serpentine which replaces 

 the Eozoon of Grenville, and also in a massive serpentine 

 from Burgess, resembling this, and enclosing fragments of 

 the fossil. In both of these specimens also grains of me- 

 chanical impurities are detected by the microscope ; they are 

 however, rarer than in the loganite of Burgess. 



" From the above facts it may be concluded that the various 

 silicates which now constitute pyroxene, serpentine, and 

 loganite were directly deposited in waters in the midst of 

 which the Eozoon was still growing, or had only recently 

 perished ; and that these silicates penetrated, enclosed, and 

 preserved the calcareous structure precisely as carbonate of 

 lime might have done. The association of the silicates with 

 the Eozoon is only accidental ; and large quantities of them, 

 deposited at the same time, include no organic remains. Thus, 

 for example, there are found associated with the Eozoon lime- 

 stones of Grenville, massive layers and concretions of pure 



