462 Dr. W. B. Carpenter on Eozoon canadense. 



supplemental [or intermediate] skeleton do not seem to be 

 directly continuous, for they are of about double the diameter 

 and lie further apart from one another ; but immediately round 

 the proper wails of the chambers there seem to be irregular 

 lacunar spaces, into which the foramina open externally, and 

 from which the passages of the canal-system originate.'' Now, 

 in my " Supplemental Notes on the Structure and Affinities 

 of Eozoon canadense " (Proceed. Geol. Soc, Jan. 10, 1866, 

 p. 222), I stated that precisely the same relation is shown to 

 exist in decalcified specimens of Eozoon^ by the implantation 

 of the dendritic models of the chamber-casts in plates formed 

 by the coalescence of the acicul^ that occupied the tubules of 

 the " proper wall." Having now been foitunate enough to 

 meet with a transparent section which exhibits this relation 

 most unmistakably (Plate XIX. fig. 1, J J), I fearlessly ask 

 the verdict of any Biologist familiar with microscopic structm'e, 

 whether any more exact realization could be presented of the 

 structure I had described in Galcarina^ — allowance being of 

 com-se made for the different scale of the tubulation of the 

 " proper wall," which is here fine " nummuline " not coarse 

 " rotaline." 



There is another feature in the canal-system of this speci- 

 men, which, by leading me to a more careful examination of 

 its ordinary distribution, has brought into view what seems to 

 me a new point of difference between the typical canal-system 

 and mineral dendritic ramifications. It will be observed that 

 the principal trunks are here in the middle of the calcareous 

 layer, the ramifications extending from them towards each of 

 its surfaces. This, of course, cannot be so clearly brought 

 out in any plane section, as it can be in such decalcified spe- 

 cimens as are represented in figs. 3,4; in which a set of canals 

 are seen to originate from the ceiling of the chamber beneath 

 them, and to converge like the roots of a tree into a stem, from 

 which diverging branches are given off towards the floor of 

 the chamber above. Now, in all dendritic ramifications I have 

 seen (I do not presume to speak with confidence of things I 

 have not seen), the branches go off from a main trunk which 

 originates at once from the source of the infiltration, instead of 

 being formed by the coalescence of roots *. I do not lay any 

 stress on the difference ; but this peculiar distribution of the 

 canal- system is not without its significance, in regard to the 



* As 1 was accustomed to see dendrites made at a Pottery in Bristol 

 forty years ago, I am not quite so ignorant in regard to them as Professors 

 King and Rowney seem to suppose that I must be, from the fact that I 

 am a Biologist and not a Mineralogist. The process was simply this : — 

 The cylindrical " biscuit" beer-cup (sold for a penny) having been dipped 



