508 



Canada. Out of the latter region, however, the laminated one appears 

 to be very rare. 



Entire specimens of the laminated variety have been found some 

 inches in thickness, and several in diameter, which has given rise 

 to the idea that individuals of " Eozoon Canadense" grew during some 

 (the early) portion of their life by the addition of tier upon tier 

 of "chambers" or "cells;" but as many specimens show this 

 variety, with the presumed representatives of the latter parts, breaking 

 up and becoming scattered through the calcareous matrix, it has been 

 considered that the "acervuline" mode of growth supervened. 



In " eozoonal" parlance the calcareous portion is named the "in- 

 termediate" or " supplemental skeleton ;" while the granules and 

 plates of serpentine are called "chamber casts," on the view that 

 they were originally cavities in the skeleton, tenanted by the sarcode- 

 divisions of the animal, and which had become filled up with a mineral 

 deposit. 



To examine specimens with a high magnifying power, it is neces- 

 sary to decalcify them with weak acid, or to prepare thin sections. 

 By the first process the calcite disappears, leaving the serpentine 

 untouched. The interspaces between the granules and plates of the 

 latter mineral are now seen to be in numerous instances crowded with 

 a great variety of simple and arborescent vermicular shapes, composed of 

 the same, or a related silicate : some are attached to the granules ; 

 and others still remain imbedded in the undissolved portion of the 

 "skeleton," seemingly independent of the "chamber casts." These 

 structures were first detected by Dr. Dawson, who, supposing them to 

 be casts of tubes, such as belong to the "canal system" excavated in 

 the "intermediate skeleton" of certain genera of foraminifers, considers 

 them to represent the same part in " JEozoon." Applying a high 

 power to the serpentine granules, &c, they are often seen to be 

 covered with a white glistening asbestiform layer, the fibres being 

 frequently at a right angle, and occasionally oblique, to the surfaces 

 to which they are attached. The fibres in many cases have a striking 

 resemblance to casts of the perforations or minute tubuli belonging to 

 the " true wall" of the nummuline foraminifers (in which the perfo- 

 rations admit of the extrusion of the sarcodic extensions, called 

 pseudopods) ; and they have consequently been considered by Dr. 

 Carpenter, to whom is due the chief merit in discovering them, to 

 represent the " nummuline layer." 



The object of our Paper was to show that every one of the struc- 

 tures diagnosed for " Eozoon Canadense" by Dawson and Carpenter is 

 purely of inorganic origin. We maintained that the " chamber casts" are 

 simply granules of serpentine — as much mineral products as the 

 grains of chondrodite, pargasite, &c, common in certain rocks ; that 

 the "intermediate skeleton" is their calcareous matrix, as is the calcite 

 in which the latter minerals usually occur ; that the branching shapes, 

 which constitute the " canal system" and penetrate the matrix, are 

 nothing more than forms of metaxite, or some allied mineral, also oc- 



