ORDER ir FOEAMTNIFERA 19 



Comparatively little is known concerning the animal of the Foraminifera 

 except in certain littoral species. As single-celled animals the Foraminifera 

 are especially interesting, and their structures do not need explanation on the 

 basis of organs or tissues. There is much beauty in the curves of the test 

 and in its ornamentation, the patterns of the latter being often very inti'icate. 



Throughout the group of Foraminifera there is a nearly complete series, 

 from a simple gelatinous covering of the cell in some of the fresh-water forms 

 to the complex calcareous test of the higher groups. The fresh-water forms, 

 while not considered in the systematic part of this treatise, are nevertheless of 

 especial interest on account of their primitive characters. In Myxotheca the 

 simplest sort of covering is found, a gelatinous test which is flexible, so that 

 it takes the shape of the changing form of the cell. There is here also no 

 definite aperture, the pseudopodia being pushed through at any point. In 

 others of the fresh-water forms the test may be of flexible chitinous material, 

 but has a definite shape when the animal is at rest and usually one or more 

 definite and permanent orifices. 



In the marine species, which form the basis of the present work, there is 

 usually a definite, specific form to the test, and the aperture is permanent. 

 The materials used in making the test may be grouped in two classes: (1) 

 those derived from foreign sources, and (2) those secreted by the animal itself. 

 The foreign materials are derived from the bottom on which the animal lives, 

 and therefore even in the same species found under diff'erent conditions there 

 is some variation in the character of the materials used. In general, however, 

 there seems to be a certain amount of selective power on the part of certain 

 forms, and such characters have been used as of generic rank in systematic 

 work. The foreign material most frequently used is the mud or sand of the 

 ocean bottom, but certain forms use sponge spicules, either making them into 

 a soft felted mass (Pilulina) or arranging them in a definite manner and firmly 

 cemented {Technitella). Other foraminiferal tests may be used, as may various 

 small bodies which come within the range of the animals. The cement in the 

 agglutinated tests may be chitinous, of iron oxide, or calcareous. 



Of these calcareous tests two sorts have been recognised, one with a definite 

 aperture or series of apertures and with minute pores (the perforate group), 

 the other with a definite aperture or series of apertures but without minute 

 pores (the porcellanous group). By many writers the latter group, represented 

 by the Miliolidae, has been held to be primitive and a group which had not 

 developed perforations.. On the other hand, certain evidence, such as the 

 perforate condition of the early chamber of Peneroplis and other genera, would 

 indicate that they are derived from the perforate group, and that the lack of 

 pores instead of being a primitive condition may in reality be a specialised 

 one derived from a condition in which pores were developed throughout the 

 life of the individual. 



In general the test of the Foraminifera may be single-chambered or many- 

 chambered. Contrary to the impression given by certain works on the group, 

 the process of adding chambers in the Foraminifera, while superficially like 

 budding or gemmation, is not necessarily or usually accompanied by nuclear 

 divisions. That is, instead of the new chambers being potential individuals 

 they are simply integral parts of one cell, and in the uninucleate form the 

 single nucleus is found in about numerically the middle chamber. In the 

 process of adding a new chamber a portion of the protoplasm is protruded 



