WHAT IS EOZOON ? 77 



the laminsB diverge from and approach each other, and fre- 

 ([uently anastomose or are connected by transverse septa. 



" Under the microscope the resemblance to Stromatopora is 

 seen to be in general form merely, and no trace appears of the 

 radiating pillars characteristic of that genus. The lamina of 

 serpentine and pyroxene present no organic structure, and the 

 latter mineral is highly crystalline. The laminse of carbonate 

 of lime, on the contrary, retain distinct traces of structures 

 which cannot be of a crystalline or concretionary character. 

 They constitute parallel or concentric partitions of variable 

 thickness, enclosing flattened spaces or chambers, frequently 

 crossed by transverse plates or septa, in some places so 

 numerous as to give a vesicular appearance, in others oc- 

 curring only at rare intervals. The laminae themselves are 

 excavated on their sides into rounded pits, and are in some 

 places traversed by canals, or contain secondary rounded cells, 

 apparently isolated. In addition to these general appearances, 

 the substance of the laminse, where most perfectly preserved, 

 is seen to present a fine granular structure, and to be pene- 

 trated by numerous minute tubuli, which are arranged in 

 bundles of great beauty and complexity, diverging in sheaf- 

 like forms, and in their finer extensions anastomosing so as to 

 form a network (figs. 10 and 28). In transverse sections, 

 and under high powers, the tubuli are seen to be circular 

 in outline, and sharply defined (fig. 29). In longitudinal 

 sections, they sometimes present a beaded or jointed appear- 

 ance. Even where the tubular structure is least perfectly 

 preserved, traces of it can still be seen in most of the slices, 

 though there are places in which the laminas are perfectly 

 compact, and perhaps were so originally. 



" With respect to the nature and probable origin of the 

 appearances above described, I would make the following 

 remarks : — 



" 1. The serpentine and pyroxene which fill the cavities of 

 the calcareous matter have no appearance of concretionary 

 structure. On the contrary, their aspect is that of matter 

 introduced by infiltration, or as sediment, and filling spaces 

 previously existing. In other words, the calcareous matter 



