538 DE. CAEPENTEE'S EESEAECHES ON THE FOBAMINIFEEA. 



figure, not merely of the shell, but also of the pseudopodia protruded from various parts 

 of its surface ; as well as to make preparations of the sarcode-body of the animal, by 

 dissolving away the shell in dilute acid. He does not seem, however, to have had the 

 advantage of a full knowledge of Professor WILLIAMSON'S memoir; his acquaintance 

 with it being apparently limited to the abstract of it contained in ' L'Institut' (No. 787) ; 

 and I find in his description of the shell a confirmation of the belief I have already had 

 occasion to express, that he has not availed himself as fully as is desirable of the mode 

 of examining the intimate structure of these minute objects by the preparation of very 

 thin sections. In every point, in fact, in which he differs from Professor WILLIAMSON, 

 I am satisfied that the truth lies with the latter ; and this not merely on account of the 

 entire coincidence between the results of my own inquiries into the structure of Poly- 

 stomella crispa and those of my accomplished predecessor, but also because our views 

 are in every respect borne out by the structure of the much larger and more highly 

 developed form of Polystomella which I am presently to describe. One point in Pro- 

 fessor SCHULTZE'S description, however, requires special notice. He states that each of 

 the crenulated prominences which are seen on the surface of the lateral walls of the 

 chambers is traversed longitudinally by a wedge-shaped fissure, that is narrowest as it 

 approaches the septal band, near which it penetrates the cavity of the chamber, whilst 

 it becomes shallower as it widens out at the part where the crenulation merges in the 

 smooth wall of the shell. I expect to be able to show that the supposed " fissures " of 

 Professor SCHULTZE no more communicate with the cavity of the chambers, than do the 

 "fossettes" of M. D'ORBIGNY; but that they are really the outlets of the canal-system, 

 whose existence in Polystomella has not been discovered either by Prof. SCHULTZE or by 

 Prof. WILLIAMSON, but which attains an extraordinary development in the type which 

 has specially fallen under my observation. 



178. The specimens of Polystomella, of which I have now to give an account, were 

 chiefly collected by Mr. JUKES in his Australian dredgings ; I have met with the same 

 form, however, in Mr. CUMING'S Philippine collection ; and I have reason to believe it 

 to be generally diffused through the Indian and Polynesian seas. It seems to be the 

 P. craticulata of FICHTEL and MOLL. The empty shells are occasionally the subjects of 

 that very curious infiltration of silicate of iron, to which attention was first directed by 

 Professor EHRENBERG as a peculiar mode of fossilization of Foraminifera, causing in- 

 ternal " casts " of their chambers to be preserved long after their shells have been 

 destroyed, in his memoir ' tlber den Gruensand und seine Erlauterung des organischen 

 Lebens"*, and which was soon afterwards shown by Professor BAILEY f to be taking 

 place at the present time over certain parts of the ocean-bottom. I have recently been 

 enabled, through the kindness of Mr. W. K. PARKER, to examine a number of most 

 perfect and beautiful " casts " which he has obtained, not merely of fragments, but of 

 the entire animal of this type of Polystomella, by treating with dilute acid shells which 



* Abhandlungen der Konigl. Akad. der Wissenschaften, Berlin, 1855. 

 t Quarterly Journal of Microscopical Science, vol.Y. p. 83. 



