AND ITS INTERNAL STRUCTURES. 315 



No authorities or references are quoted for this latter state- 

 ment — an unfortunate omission. In their absence we must suppose 

 that Sir John Murray's record of the occui-rence of the monadi- 

 form bodies in the balloon chamber is alluded to, though the 

 substitution of " embryonic shells " for " microspores," which the 

 monadiform bodies doubtless were, seems unjustifiable. 



It will thus be seen that since d'Orbigny first described 

 C. hidloides in 1839, two additions only have been made to our 

 knowledge. Moebius discovered the tube leading into the interior 

 of the balloon, and Murray the constant presence of monadiform 

 bodies or microspores in the sarcode of the balloon chamber. It 

 will also be seen that all the writers who have described the form 

 speak of the balloon as a single enlarged chamber. As a matter 

 of fact this final inflated portion of the shell is double, and 

 consists of two chambers, one within the other, and having no 

 connection with each other. This is clearly shown in the 

 specimens exhibited on the table, in which I have entirely 

 removed the whole of the outer covering (the " balloon " of 

 Brady), leaving the inner chamber, which I propose to call the 

 "float " chamber, quite perfect and intact. 



This inner or •' float " chamber is a very singular feature, and 

 I believe quite unique in its structure and delicacy. It occupies 

 nearly the whole of the interior of the balloon, in which it hangs 

 suspended, but is not attached to the inner surface of the balloon 

 in any way. It is attached to the lower surface of the upper or 

 spiral shell, but it has no direct connection with these upper 

 chambers, the only opening into its interior consisting of the 

 small tube in the centre of its base, discovered by Moebius. This 

 tube is not in any way connected with the external or balloon 

 chamber, the inner surface of the base of the balloon being 

 perfectly smooth except for the large " orbuline " pores. 



In shape the " float " chamber varies considerably in diflferent 

 specimens. In Mr. Matthews' specimens, and in most small 

 shells, it is almost perfectly globular, and exhibits none of those 

 constrictions of the surface which are characteristic of the *' float '^ 

 chamber in large and mature shells. These constrictions, which 

 start from the point of attachment of the " float " chamber, are 

 often so deep and marked as to give a distinctly lobate appearance, 

 so that the " float '' chamber bears some resemblance to a tomato 

 or to a bag of wet sand tightly bunched together at the top. 



