14: 



THE MICROSCOPE AND ITS REVELATIONS. 



parts of the Continent, and also (by Mr. Archer 1 ) in Wales and Ireland; 

 occurring chiefly in dark ponds shaded by trees and containing decaying 

 leaves. Its soft sarcode body is incased by a siliceous capsule of spheri- 

 cal form, regularly perforated with oval apertures, and supported on a 

 long silicified peduncle. The body itself, and the pseudopodia which it 

 puts forth through the apertures of the capsule, seem closely to corre- 

 spond with those of ActinopJirys. Eeproduction here takes place not 

 only by binary fission, but by the formation of 'swarm spores.' In the 

 first mode, one of the two segments remains in possession of the silice- 

 ous capsule, whilst the other finds its way out through one of the aper- 

 tures, lives for some hours in a free condition as an Actinophrys, and 

 ultimately produces the capsule and stem characteristic of its type. In 

 the second mode, numerous small rounded sarcode-masses, each possess- 

 ing a nucleus, are produced within the capsule, in what manner cannot 



FIG. 287. 



Marginal portion of Actinosphcerium Eichornii, as seen in optical section under a higher mag- 

 nifying powder: m, endosarc; r, ectosarc; a, a, a, pseudopodia; n, n, nuclei with nucleoli ; /, 

 ingested food-mass. 



be clearly made-out; and every one of these is enveloped in a firm envel- 

 ope, set round with short spines, probably siliceous. These cysts remain 

 for months within the common capsule; and when the time arrives for 

 their further development, the sarcode-corpuscles slip out of their cysts, 

 and escape through the orifices of the capsule as flagellated Monads of 

 oval form (Fig. 288, B,) each having a nucleus, n, near the base of the 

 flagella, and two contractile vesicles near its opposite end. After swarm- 

 ing for some hours in this condition, they change to the free Actinophrys 

 form, and finally acquire the siliceous capsule and stem of the Clathru- 

 lina. 



403. Lobosa. No example of the Rhizopod type is more common in 



1 See his Memoir on Fresh-water Radiolaria in "Quart. Journ. of Micros. 

 Sci.," N.S., Vol. ix. (1869), p. 230. 



