100 NOTES AND MEMORANDA. 



Perforata, after Carpenter. The latter mode appears not 

 only more generally recognised, but, from a scientifie point 

 of view, more to be commended. In Carpenter's system the 

 f.ieshwater Monothaliama would self-evidently have to be 

 relegated to the Imperforata beside Gromida. The number 

 of nuclei having evidently no relation to the number of 

 chambers, it is, without doubt, that the latter can be re- 

 garded as but an external jointing of the shell, without any 

 definite relation to the sarcode body. 



In conclusion, the author recapitulates the characteristics 

 of the 



Thalamophora. 



They are organisms whose soft body consists of undifferen- 

 tiated sarcode, sending out changeable processes of the most 

 different form — Pseudopodia — for the purpose of locomotion 

 and capture of food. Cell-nucleus, single in young organ- 

 isms, but may extraordinarily increase in the course of 

 growth. 



Fluid aggregations are almost constantly present in the 

 interior of the body, either in the form of simple vacuoles 

 or of contractile "vesicles." 



All Thalamophora possess a skeleton, which is either 

 purely chitinous or impregnated with lime, or covered with 

 silicious particles. Its characteristic is the monaxial funda- 

 mental form ; that is, a principal axis of the shell can be 



constantly recognised This principal axis is in the 



simpler cases straight (Gromia, Nodosarin), in most cases 

 spirally curved (Miliola, Kotalia, Polystomella, &c.) ; fre- 

 quently this curvature takes place very irregularly, and gives 

 rise to the appearance of a seemingly clustered arrangement 

 of the sections of the shell, as if without rule (Acervulina). 



By means of constrictions running vertically to the axis 

 the shell may be subdivided into sections, one behind another 

 (chambers), which may stand in mutual connection after 

 very different modes (Polythalamatous forms). 



According to the structure of the shell the author would 

 divide the class into the two orders : 



1. Imj)erforata. 



No communications between the cavity of the shell and 

 the outer world other than the constantly considerable 

 shell-opening. 



2. Perforata. 



Numerous fine foramina perforate the shell- wall; hence 

 the shell-opening proper is mostly minute and rudimentary. 



