50 FRESH-WATER RHIZOPODS OF NORTH AMERICA. 



noticed in the enclosure, from the side of the posterior narrow end ; and 

 the A. verrucosa, within its now globular water-vacuole, had become bent 

 upon itself, as' seen in fig. 18. Still later, the body of the A. verrucosa 

 appeared to have become broken up into five spherical, granular balls, as 

 seen in fig. 19, which rolled about among the other constituents of the 

 endosarc of the A. proteus. These observations were conducted through 

 about seven hours. What finally became of the five balls resulting 

 from the destruction of the A. verrucosa I did not ascertain, but sup- 

 posed that they were digested, to contribute to the nutrition of the Amoeba 

 proteus. 



In my studies of Amoeba proteus I have not been so fortunate as to 

 trace its history from an early period, nor to discover its modes of repro- 

 duction. In association with the more characteristic forms, I have seen 

 many which I have suspected to be the young ; but it is quite as probable 

 that they may have pertained to other described species. 



Comparatively small Amcebas are frequently to be met with, which, 

 though exhibiting considerable variety, are yet commonly and habitually 

 clavate, or more or less slug-like in shape. Similar Amoebae have been 

 described under the names of Amoeba Gleichenii, A. Umax, A. guttula, etc. 



Some of these I have suspected to be the young of Amoeba proteus, 

 though with equal probability they may be considered to belong to some 

 other species. They are usually quite active, and glide along with the 

 thicker extremity in advance, with comparatively little change of form. 

 The posterior extremity is more or less tapering, and terminates bluntly, 

 and mostly without any process, though the end is apparently in some 

 degree prehensile, as it is occasionally observed with adherent materials 

 dragged after the animal in its movements. 



Do 



Progression commonly is due to an incessant, more or less even, or 

 interrupted, flow or roll of the ectosarc of the head end forward, followed 

 closely by an influx of the endosarc and a concurrent contraction of the 

 body behind. The precession of the ectosarc at the head end appears as 

 a clear watch-crvstal-like extension of variable thickness, into which the 

 endosarc flows from one side and spreads towards the other. Frequently 

 the onward movement of the animal is promoted by the projection of 

 hemispherical pseudopodal lobes, alternately and in succession, at the sides 

 of the head end, which are produced in the same manner as the latter itself. 



