THE AJICEBA. 



335 



Organic morsels over which these Amcebce softly glide are taken into the plastic body, sometimes 

 at any spot, but generally at a particular region, where the clear sarcode is thinnest; and water is 

 also absorbed or enclosed. Thus the acts of eating and drinking, without mouth and stomach, are 

 accomplished ; and assimilation (rather than digestion) of the good and available portions of the prey 

 duly takes place. 



After continued growth, the body sometimes divides into two living individuals ; but it often 

 becomes almost wholly a mass of zoospores, so that the once unicellular creature is converted into an 

 uncountable multitude of living " cells " or simple animals. 



Thus also the " cells " in our own bodies play their part ; multiplying new " cells," and 

 replacing those which have been used up. More espe- 

 cially the white globules of the blood of animals are 

 amoeboid. As they circulate along the vessels, they 

 execute movements like those of Amcsbcr, ever modi- 

 fying their shape ; and they can be made to enclose 

 foreign substances (such as carmine), just as the Amoeba 

 takes in its food. Further, a simple Amteba has a strik- 

 ing resemblance to the " primary cell " or " ovum " of all 

 animals, whether vertebrate or invertebrate. It may be 

 regarded as equivalent to this unicellular phase of higher 

 organisms. As a vital mass of the simplest and most 

 elementary formation we can conceive, it is adapted for 

 a very low stage of existence, having only the properties 

 of locomotion, assimilation, and reproduction. Having 

 such an extremely rudimentary formation, many of the 

 Protozoa have been regarded as members of the Vegetable 

 Kingdom, and as mere germs of some plants. Haeckel 

 places many of thenr, as Protista, in an intermediate 

 position. The Amoeba, however, and its numerous allies, 

 prey on organic substances, and even on living organisms, 

 after the manner of animals. But in this great group 



they take their place, in classification, according to the relative absence of those special organs which 

 characterise the higher members of the kingdom. 



VI. The sarcode of the Amoeba is often yellowish from its contained granules ; but it is nearly 

 transparent at one, usually the broader, end of the body in active individuals ; whilst the granules, 

 germinal and other globules, and particles of food, more or less digested, with green, yellow, brown 

 and other tints, crowd and darken its hinder part. The edge of this, under the microscope, looks like 

 a pellucid coat (in section) by transmitted light ; and being free from coarse particles, invests, as it 

 were, the thicker interior with a thin layer of sarcode. The more coarsely granular and inner 

 material is called the " Endosarc ;"* the other is the "Ectosarc,"t or "Diaphane."| They are really 

 interchangeable ; the outer surface, which is toughish, without being coated with any membrane, may 

 be turned in and becomes as soft as the rest of the sarcode, especially when the prey is engulfed and 

 takes in some of the inturned ectosarc with it. 



The contents of the endosarc appear to be : 1. Granules of various kinds some exceedingly 

 minute and protoplasmic, others relatively large, some of which are apparently like water, some like 

 oil, some like starch ; 2. Newly ingested food some soft (Desmids, &c.), some hard (Diatoms) and 

 food-balls of partly digested food, which soon become broken up as loose particles in the endosarc ; 

 3. Water- vacuoles, either independent or investing morsels of food, and probably arising from water 

 engulfed either by itself or with the food ; 4. Quartz sand sometimes, and " in some fine, large, 

 vigorous specimens of A. protem, collected from a pond in the vicinity of a saw-mill," Dr. Leidy found 

 that " the endosarc contained multitudes of particles of sawdust ; " 5. Minute crystals, regular in 

 form (octahedrons and others) ; 6. Sarcobksts ; 7. The nucleus ; and, 8, the pulsating or contractile 

 vesicle. There may be more than one of each of these. 



* Greek, avion, within ; sarx. fesa. f Greek, ektos, outside ; sarx. I Greek, diaphancs, transparent. 



Fig. 3. AM<EBA PROTEVS, WITH PSEUDOPODIA 



ADVANCED TO THE UIGHT, AND A LARGE 

 XAVICULA ENVELOPED IN THE DISTENDED 

 HINDER PART. THE PAPILLARY OR MUL- 

 BERRY-LIKE EXTREMITY IS SEEN TO THE 

 LEFT OF THIS. 



n, Nucleus; cr, contractile vesicle: the dark spots art- food 

 tails and food vacuoles. Magnified a.0 diameters. After 

 Leidy.t 



