198 PEOF. W. J. SOLLAS OX SACCAMMIXA CARTE HI, [vol. Ixxvii, 



The striking difference in the outward appearance of the Per- 

 forate and the Imperforate shell is due to an equally striking 

 difference in their minute structure. 



The structm-e of the Imperforate shell is, however, by no means 

 what is generally supposed. As seen hj ordinary light under the 

 microscope a thin section of such a form as Orbitolites, ior insiance, 

 presents much the same appearance as chitin, and it was quite 

 natural that the earlier observers should have concluded that the 

 shell consists of a basis of this substance impregnated with 

 carbonate of lime. 



On decalcification with dilute acid an organic residue is obtained 

 which retains the form of the shell. It consists most obviousl}^ of 

 a delicate membrane or cuticle, which lines the walls of the 

 chambers and invests the interior of the shell. In ordinary 

 circumstances nothing more is visible ; but, with appropriate treat- 

 ment — staining with methylene blue — a delicate network is 

 revealed, which extends through the substance of the shell from the 

 lining membrane on one side to that on the other. This was first 

 shown by F. Schaudinn ^ in his study of Calcitiiha, and sub- 

 sequently by S. Awerinzew ^ in Peneroplis and Miliolina. Con- 

 firmatory observations were afterwards made by F. W. Winter.^ 

 Stress has been laid by those authors on the facility with which 

 this network may escape observation. This accords with my own 

 experience. Some specimens of Orhitolifes from Fiji,'^ gathered 

 fresh from fronds of seaweed and preserved in the dried state, were 

 slov/ly decalcified, stained with borax carmine, and cut in serial 

 transverse sections 6 ^ thick. The protoplasm of the chambers 

 was shown deeply stained and surrounded by the lining membrane, 

 which was also stained, but less deepl}^ The place previously 

 occupied by the calcareous skeleton, however, seemed to be empty 

 of all but balsam. The sections were then treated with methylene 

 blue, which at once revealed the presence of a fine network in the 

 apparently empty space. My friend Prof, Goodrich, who applied 

 this stain for me, then treated the sections with Stephens's blue- 

 black ink, which rendered the network remarkably conspicuous. 



On the other hand, specimens of Miliola, gathered from Coral- 

 lines at Lyme Regis, killed with corrosive sublimate and preserved 

 in alcohol, showed after similar treatment scarcely a trace of the 

 intraskeletal network, although the lining membrane was well 

 displayed.''' 



^ ' Untersuchungen an Foraminiferen : I — Calcituha polymorplia Eoboz ' 

 Zeitschr. f. Wissensch. Zool. vol. lix (1895) p. 219. 



2 ' Ueber die Struktur der Kalkschalen Mariner Rliizopoden ' Zeitschr. 

 f. Wissensch. Zool, vol, Ixxiv (1903) p, 478. 



•^ ' Zur Kenntniss der Thalamophoren ' Archiv fiir Protistenkunde, vol. x 

 (1907) p. 41, 



^ My best thanks are due to my friend, Sir Sidney Harmer, for the gift of 

 these and other specimens, 



^ I am indebted for this and many other specimens to the generosity of my 

 friend, Dr. J. J. Lister. 



