200 ME. E. B. WETHERED ON THE [May 1895, 



present in two conditions, namely, the granular amorphous, repre- 

 senting infilling or secreted material ; and the non -crystalline clear, 

 indicating the organic or structural portion of the granule. 



One interesting feature in this granule is that the inner and outer 

 crusts are quite independent. At first this granule consisted only 

 of the central nucleus and the inner crust, and in this condition 

 appears to have undergone a certain amount of erosion, evidence of 

 which we get in the two depressions at the top. After a time this 

 inner granule became a nucleus for the outer crust, which seems to 

 have commenced by one or two tubules attaching themselves to the 

 inner crust, and finally developing into the irregular concentric 

 laminated growth represented by the outer crust. 



I cannot leave this granule without pointing out how inconsistent 

 the irregularity of tbe laminae in the crust is with the chemical 

 theory of the formation of oolitic granules. We can scarcely 

 imagine that deposited strata of calcium carbonate could assume 

 the irregularity and general appearance which this presents. On 

 the other hand, the features are consistent with the growth of such 

 low forms of life as the calcareous algse. 



PI. VII. figs. 4 a and 4 b. — These illustrations represent a section 

 of a granule looked at end-ways; fig. 4 a is drawn from a positive 

 photograph, fig. 45 from a negative. 



Signs of concentric structure are present at the top and bottom of 

 this granule, but the main portion of the crust shows a radiating 

 structure. Around the nucleus there are patches of amorphous 

 calcium carbonate which extends into the radiating structure, and 

 is either concretionary or infilling-material. This is best seen in 

 fig. 4 b. 



PI. VII. fig. 8. — This is a form of granule met with in the Coral- 

 line Oolite. In the centre are masses of minute tubules which are 

 recognized as belonging to GirvaneUa. Some of these appear in 

 horizontal section, some in vertical. Each one is defined by a dark 

 wall on either side, and the centre is filled in with light and dark 

 material. This aggregation of inner tubules forms a nucleus for 

 a crust wherein occur tubular objects which exactly resemble the 

 GirvaneUa in the centre of the granule, except that they are larger 

 and grow concentrically. There are also spaces in which no 

 structure is visible. 



In support of the view that these concentrically growing objects 

 are tubular forms of growth, I would point out that each is 

 bounded by walls, and that the interiors are filled in with light and 

 dark material, precisely as we find the case to be with Girvanella- 

 tubules. It may be argued that these objects are organic bodies 

 which have been enclosed by an inorganic crust, and in support 

 of this the fact that the growth is not continuous may be cited. 

 In answer to this objection I would say that at one point the 

 outlines of tubules are visible, though very indistinct. This is 

 evidence of the obliteration of these frail objects, which would 



