THE FORAMINIFERA. l6l 



In classifying the Foraminifera the first great distinction 

 which strikes the observer is their division into one-celled 

 {Monothalamia) and many-celled (Polythalamia). The ani- 

 mals, being all of one sarcode-like substance, exhibiting the 

 same habits of life, cannot as with the higher orders, such as 

 the Mollusca be taken into any, or for more than a very little 

 account for generic or specific distinction. The characters of 

 the shell are therefore looked to as a basis of classification, the 

 form and arrangement of the cells or chambers, the mode of 

 their connection, the presence or absence of large or small 

 openings, their markings, and the intimate structure of the 

 shell, are the principal points for consideration. The Forami- 

 nifera are thus arranged into families, genera, species, and 

 varieties. Our knowledge of them, it must be confessed, is 

 unsatisfactory and imperfect ; gradually, however, no doubt 

 they will be better understood, as they are now receiving a 

 considerable amount of attention from eminent naturalists. 

 Theories and classifications are, by observation and research, 

 being continually modified and altered ; but one fact is uni- 

 versally observed, and that is the variableness of these minute 

 creatures. In several species a definite type of form prevails, 

 or rather the idea of it, whilst scarcely two shells will be found 

 identically the same. I have noticed this particularly in the 

 Miliolince, which are exceedingly abundant on our shore. Dr. 

 Carpenter says, " The range of variation is so great among 

 Foraminifera as to include not merely the differential charac- 

 ters which systematists, proceeding upon the ordinary methods, 

 have accounted specific, but also those upon which the greater 

 part of the genera of this group have been founded, and even 

 in some instances those of its orders. The ordinary notion of 



