and Reproductive Phenomena of the Amoeban Rhizopods. 467 



visible within the body. Average diameter of component gra- 

 nules 1 2Woth of an inch. 



Fig. 7. The same specimen as seen after the completion of the fourth stage 

 of its development. The character of the acapsular nucleus is now 

 entirely lost, through the diffusion of its component granules 

 and the increase of the more hyaline protoplasm. Contractile 

 vesicles (c) now in constant action. A nucleus, similar in all 

 respects to that seen in the former specimens, is also present. 

 Size now variable, and dependent on form assumed for the time 

 being. When globular, about g-s^oth of an inch. 



Fig. 8. An occasional variety of the kind shown in the last figure, in which 

 the oi'iginal acapsular nuclear mass (ra) remains nearly entire, the 

 ordinary minute encapsuled nucleus not being hitherto observ- 

 able, h, a number of the large hexahedral crystalloids, vary- 

 ing from j^V Tyt^ to -^^-QT^th. of an inch in length. These cry- 

 stalloids, however, are not confined to the specimens exhibit- 

 ing the peculiar condition of the primary acapsular nucleus, but 

 are occasionally to be met with in the ordinary young Amabcc. 

 Length of specimen about eas^h of an inch. 



Fig. 9. A frequent form, in which the normal condition of the nucleus is 

 shown, but the pseudopodia have temporarily assumed the taper- 

 ing and pointed shape. 



Fig. 10, Amce,ba-cysi from damp confervoid growths liable to desiccation, 

 shown as it appears after immersion in water. Contractile ve- 

 sicle (c) dilated, but imable to discharge in the usual manner. 

 ss, sarcoblasts ; d, an effete frustule of a diatom {Nitzschia am- 

 phioxys). Diameter of cyst about 2 o^th of an inch. 



Fig. 11. Remarkable quiescent state oi Amceba viUosa,m which the surface 

 is covered with more or less rigid, short, tapering pseudopodia of 

 an Actinophryan character. Length, as seen in figure, about v^g^tb 

 of an inch. Diameter of nuclear capsule ^xroth of an inch ; of 

 nucleus jjVoth- 



Figs. 12 to 15 represent successive stages in the encystation of Amoeba. 



Fig. 12. A specimen becoming quiescent, after having incepted a large 

 Pinnularia and thrown off all other extraneous substances, — 

 the nucleus and its capsule being either absorbed, rendered 

 invisible amongst the granules, or entering partly into the com- 

 position of the granular mass, of which the entire body now 

 seems to consist. Some large oil-globules are shown within the 

 diatom-frustule ; c, minute contractile vesicles, the action of 

 which is almost wholly suspended. 



Fig. 13. The same form, showing the Actinophryan pseudopodia retracted, 

 and the margin of the body rapidly becoming smooth and 

 oblong. 



Fig. 14. The membranous Amoeba-cyst now complete, the granular par- 

 ticles of which the substance of the body was composed having 

 become segregated into masses which take the form of sarco- 

 blasts. 



Fig. 15. The contents of the Amceba-cyst have now almost entirely disap- 

 peared, but within the dehiscent valves of the diatoms are to be 

 seen the sarcoblasts. This last condition is, comparatively, of 

 rare occurrence. The average length of the four specimens here 

 delineated was about g^l^th of an inch. 



Fig. 16. Test of Difflugia pyriformis, var. symmetrica (Wall.), showing 

 symmetrical arrangement of the crystalline plates. 



Fig. 17- Group of minute Amoeba, each developed from a single granule 



