22 



THE MICROSCOPE AND ITS REVELATIONS. 



in contact with it; for such change of place as the animal does exhibit, 

 is effected by the contractions and extensions of the body generally, as 

 in Amoeba ( 403). An 'encysting process/ very much resembling that 

 of the lower Protophytes, is occasionally observed to take place in Gre- 

 garincB 9 and seems to be preparatory to their multiplication. Whatever 

 the original form of the body may be, it becomes globular, ceases to 

 move, and becomes invested by a structureless 'cyst/ within which the 

 substance of the body undergoes a singular change. The nucleus dis- 

 appears; and the sarcodic mass breaks up into a series of globular parti- 

 cles, which gradually resolve themselves (as shown at B, c) into forms 

 very like those of Naviculce. These ' pseudo-navicellse ' are set-free, in 

 time, by the bursting of the capsule that incloses them; and they develop 

 themselves into a new generation of Gregarinae, first passing through an 

 Amoeba-like stage. A sort of 'conjugation' has been seen to take place 

 between two individuals, whose bodies, coming into contact with each 



FIG. 294. 



Gregarina of the Earthworm: A, in its ordinary aspect; B, in its encysted condition; c, D, show- 

 ing division of its contents into pseudo-navicellae; E, F, free pseudo-navicellae ; o, H, free amoeboids 

 produced from them. 



other by corresponding points, first become more globular in shape, and 

 are then encysted by the formation of a capsule around them both; the 

 partition-walls between their cavities disappear; and the substance of 

 the two bodies becomes completely fused together. But as the product 

 of this 'zygosis' is the same as that of the ordinary encysting process, 

 there seems no sufficient reason for regarding it, like the ' conjugation ' 

 of Protophytes, as a true Generative act. 



Prof. Haeckel's Memoirs on Jtfonera and the Gastrcea Theory will be found in 

 the successive Nos. of the " Jenaische Zeitschrift" beginning with 1868; and in 

 a collected form, in the two parts of his " Biologische Studien." The first of 

 his Memoirs on Monera is translated in " Quart. Journ. Microsc. Sci.," N.S., Vol. 

 ix. (1869); and the first of his Papers on the Gastrcea Theory in Vol. xiv. (1874) 



