DR. SCHULTZE, ON THE RHIZOPODA. 147 



cesses are protruded throug^h a large opening in the mem- 

 branous, chitinous test. In Ai^cella this test is soft and 

 flexible, and in Dijflugia it is impregnated with silex (in the 

 form of arenaceous particles, Diatomace(P) ; Avhilst in other 

 forms, apparently living only in the sea, the body is enclosed 

 in a calcareous shell, though the filamentary processes exhibit 

 exactly the same phenomena as those described in Amaiha 

 porrecta. These filaments are protruded either from a single 

 large or from numerous minute openings, and are characterised 

 by the active stream of minute globules. Their length is occa- 

 sionally twelve times the diameter of the body ; they branch 

 repeatedly in their course, and are united by delicate bridges 

 and plates. The network of sarcode-substance thus produced 

 not unfrequently covers an area of several lines in diameter, in 

 the midst of which is seated the body of the animal enclosed in 

 its saccular flexible test, or in a delicate chambered shell, 

 like a spider in the centre of its web. These forms constitute 

 the testaceous Rldzojwda, and are the subject of the present 

 work. On account of their nautilus-like and chambered shell, 

 they were formerly arranged with the CejjhalojJoda, but were 

 placed in a distinct class by D'Orbigny, under the name of 

 Foraminifera. From Breyn (1732) and Soldani (1789-98) 

 they received the name of I^olythalamia, under which desig- 

 nation they were desc:ribed by Ehrenljerg as a sub-order of 

 the Bryozoa. But neither of these appellations, strictly inter- 

 preted, is applicable to the entire protozoan class of Rhizo- 

 poda ; inasmuch as they are unsuitable to the naked forms, 

 which, as we have seen, must be included in that class. 

 Either, however, might be used to designate that subdivision 

 of the class in which the soft animal is included, in a fora- 

 minated or chambered shell. 



Owing to the opacity of the shell in many of the Forami- 

 nifera, and the strong refractive power of the earthy con- 

 stituent, it is but rarely that satisfactory observations have 

 been possible in uninjured individuals. It is requisite, there- 

 fore, either by breaking the shell, or, what is better, by the 

 careful removal of separate portions of it, to expose the body 

 of the animal. And the same end may also be attained by 

 the careful application of diluted acid. By these three 

 methods it is not difficult to obtain a satisfactory view. It 

 need scarcely be remarked, that the parts external to the shell 

 can be observed without any extraneous aids of the above 

 kind, and that the observation should be made in tlie living 

 creatuie. 



The shell with which the soft substance is closely invested 

 is either flexible, or rigid, being rendered so by the deposition 



L 2 



