742 MICROSCOPIC FORMS OF ANIMAL LIFE PROTOZOA 



A large number of new and curious fresh-water forms of thi 

 type are being frequently brought under notice, of which the Clathru 

 Una eleyans (fig. 576) may be specially mentioned as presenting ai 

 obvious transition to the Polycystine type. This has been foun< 

 in various parts of the Continent, and also (by Mr. Archer J ) ii 

 Wales and Ireland, occurring chiefly in dark ponds shaded fr 

 trees and containing decaying leaves. Its soft sarcode-body, whicl 

 is not differentiated into ectosarc and endosarc, is encased by ; 

 siliceous capsule of spherical form, regularly perforated with ova 

 apertures, and supported on a long silicified peduncle. The bod; 

 itself and the pseudopodia which it puts forth through the nper 

 tures of the capsule seem closely to correspond with those o 

 Actinophrys. Reproduction 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 siliceous cap 

 sule, whilst the other finds its way out through one of the apertures 

 lives for some hours in a- free condition as an Actinophrys, am 

 ultimately produces the capsule and stem characteristic of its type 

 In the second mode numerous small rounded sarcode masses, eacl 

 possessing a nucleus, are produced within the capsule, in whal 

 manner cannot be clearly made out ; and every one of these if 



enveloped in a firm en 

 velope, set round witl 

 short spines, probablj 

 siliceous. These cyst.- 

 remain for months with- 

 in the common capsule 

 and when the time arrive.- 

 for their further develop- 

 ment the sarcode -cor- 

 puscles slip out of theii 

 cysts, and escape through 

 the orifices of the capsule 

 as flagellated monads oi 

 oval form (fig. 576, B), 

 FIG. 577. Diagrammatic representation of Amoeba eac]l havino" a nucleus 



P-;' 



VIL 



a, near the base of the 

 flagella, and two con 



proteus: E C, ectosarc; E N, eudosarc ; C V, con- 

 tractile vesicle ; N, nucleus ; P, pseudopodia ; 

 VIL, villous tuft. 



tractile vesicles near its 



opposite end. After swarming for some hours in this condition, 

 they change to the free Actinn/Jtri/s form, and finally acquire the 

 siliceous capsule and stem of the (Jlathrulina. 



Lobosa. No example of the rhizopod type is more common in 

 streams and ponds, vegetable infusions, Arc., than the Amoeba 

 (fig. 577); a creature which cannot be described by its form, for 

 this is as changeable as that of the fabled Proteus, but may yet be 

 definitely characterised by peculiarities that separate it from the 

 two groups already described. The distinction between ' ectosarc ' 

 and ' endosarc' is he-re clearly marked, so that the body approaches 



1 See his memoir on Fresh-water Kadiolaria in Quart. Journ. of Microsc. Sci. 

 n. s. vol. ix. 1809, p. 250. 



