400 PROF. TH. W. ENGELMANN. 



upon frogs' blood-corpuscles in active amoeboid movement, 

 according to Golubew,^ is that after some time (generally j — 1 

 min.) the processes at first pointed become blunted, and 

 gradually draw themselves into the cell-body. '' If the stimulus 

 acts more strongly a very rapid and complete drawing together 

 of the cell so as to form a rounded lump may be observed. 

 In this condition the cell remains for some time, and then 

 resumes its ordinary movements.'' With still stronger ex- 

 citation the cell almost always becomes suddenly spherical. 

 In a few minutes a small droplet suddenly extrudes from 

 some spot, increases in size for a time, more body sub- 

 stance flowing into it; it then decreases in size again, while 

 at one or more spots new droplets are extruded. In 

 this manner changes of form may occur which are at first 

 very rapid and striking, but soon become slower ; the 

 droplets are drawn in, and the ordinary irregularly pointed 

 processes are reformed. Fresh-water Amoebse behave in a 

 similar manner, only much more quickly .2 It must be noted 

 that after a latent period, which with weak excitation amounts 

 to some seconds but with stronger excitation may become 

 imperceptibly short, there follows a slowing, or more probably 

 a stopping altogether of the granular streaming movements, 

 and of the shifting of position. After this follows — it is appa- 

 rently simultaneous only when the excitation is very strong — 

 a withdrawal, a shortening and thickening of the processes, 

 which may amount within a few seconds to an assumption of a 

 spherical shape. Soon after this are thrown out, generally by 

 jerks, one or more hyaline protuberances into which the 

 granules proceed forthwith to stream. The latter fasten 

 themselves often to the surface of the outer pellicle. One of 

 the processes enlarges more and more, stretches itself length- 

 wise, and finally takes the whole of the mass of the protoplasm 



1 A. Golubew, ' Ueber d. Erschein., welche electrische Schlage an den Sog. 

 farblosen Bestandtheilen des Blutes hervorbringen," ' Sitzungsber. d. Wiener 

 Acad.,' Ivii, p. 557, etseq., 1868. 



^ Th. W. Engelmann, "Beitr. zur Physiol, d. Protoplasma," 'Arch. f. d. 

 ges. Physiol.,' ii, p. 312, et seq., 1869. 



