GENUS AMCEBA— AMOEBA PliOTEUS. 51 



The endosarc of the small Amcebse presents a basis of pale, indistinct, 

 granular matter, merging into the almost vanishing granular constitution 

 of the hyaline ectpsarc. Scattered through it are coarser granules with 

 variable proportions of fine oil-like molecules and darkly defined particles, 

 which in many instances appear to be crystalline in form. A conspicuous 

 contractile vesicle commonly occupies a position posterior to the middle of 

 the body, and hot unfrequently two or more of such vesicles occur. With 

 the more characteristic contractile vesicle, variable numbers of water-vacu- 

 oles frequently occur, undistinguishable from the former in appearance, 

 but with less regular or no evident rhythmical movements. A round 

 nucleus, of homogeneous granular structure, and surrounded by a clear 

 halo, is a common constituent. 



In the smallest or youngest Amoebae, food in balls or other conspicu- 

 ous form is commonly absent, though occasionally an individual may be 

 seen containing a single small diatom. 



Examples of Amcebse, viewed as probably pertaining to the young of 

 Amoeba proteus, are subjects of the following notices. 



Some water scooped from a cow-track in a marshy place, in the 

 month of Mai:ch, contained an abundance of Amoebae, together with dia- 

 toms. The smallest Amcebse, as represented in figs. 21-23, pi. VIII, 

 were ovoid, and ranged from 0.036 to 0.048 mm. in length. They moved 

 actively by repeated hemispherical bulgings, first on one and then the other 

 side of the broader end, though at times the bulgings occurred elsewhere. 



In structure, they consisted of delicate granular endosarc invested 

 with clear ectosarc. The endosarc contained coarser granules, among 

 which some appeared to be of crystalline form. There were also present a 

 nucleus surrounded with a faint halo, and a contractile vesicle. Often 

 there were two of the latter, and sometimes a greater number. None of 

 the specimens contained distinct food-balls. 



The larger Amcebse ranged in size from the former up to 0.125 mm. 

 in length. These were active and slug-like in shape, as seen in fig. 29. 

 They moved with the thicker end forward through the agency of hemi- 

 spherical pseudopodal lobes, bulging alternately at the sides of the head end. 

 They proceeded straight forward or often curved to one side or the other. 

 The endosarc contained many scattered, darkly outlined granules, which 

 appeared- indistinctly to be crystalline. It also contained many clear 



