224 



HAEDWICKE'S SCIENCE-GOSSIP. 



[Oct. 1, I860. 



scope while we watch it, at a slow but steady 

 rate. 



We observe with a one-inch power a small trans- 

 parent gelatinous body of irregular shape, only 

 rendered visible by its refractive property, differing 

 slightly from that of the water surrounding it. 

 Though there may be several individuals on the 

 slide, we should hardly recognize the being we are 

 in search of, unless a practised eye first pointed it 

 out. " When found," however, we " make a note 

 of it," and put on a higher power, say a i-inch. 

 Now we see the dim outline of a figure, somewhat 

 oval in shape, filled with moving granules of various 

 sizes, like a drop of jelly containing bubbles, &c. 

 We get out pencil and paper and commence a 

 sketch, but ere we have mapped it out, we find the 

 shape has changed from an oval to a triangle. So 

 we commence again, to be again foiled, for our new 

 acquaintance has assumed a trapezoidal form, which 

 it gradually, but rapidly, exchanges for some other. 

 Now it is long and slender; in a short time it 

 changes its shape to an irregular polygon, and anon 

 it gathers itself compactly together like a pea. All 

 these transformations are but means to an end ; 

 simply a mode of progression which more nearly 

 resembles the flowing of a thick fluid on a level 

 surface than anything else we can think of. 



Long ago, attention was drawn to these creatures, 

 which were said to be produced spontaneously in 

 water containing small fragments of decaying meat, 

 or in infusions of hay and other vegetable matters, 

 but the idea of spontaneous generation, though te- 

 naciously held still by some, has few advocates of 

 late, and we now know that the amoeba is as much 

 a denizen of the ponds and ditches, as are the 

 sticklebacks and the snails, and also, that the germs 

 of microscopic organisms are present in the atmo- 

 sphere, ready to develop themselves wherever they 

 find a suitable nidus. 



Fig. 208. Amoehu villosa x 239. 



The substance of which the Amoeba is composed 

 is called sarcode, and it is considered by the most 

 competent observers that the outer portion differs 

 somewhat from the inner. The former (called ecto- 

 sarc), is " clear, transparent, and colourless, con- 

 taining, permanently, few or no granules, or foreign 



bodies of any kind, " * and capable of extension in 

 any direction to a surprising extent, thus forming 

 false feet or pseudopodia, while the latter, which 

 follows the contour of the ectosarc, is filled with a 

 vast number of granules, consisting chiefly of food 

 in course of being digested. f There may also be 

 noticed in the greater number of instances a glo 

 bular transparent body enclosed in the sarcode, near 

 a villous patch of uncertain nature, often occirrring 

 in specimens, and this is believed to be the egg or 

 young amoeba. It has been seen iu the act of being 

 discharged from the parent — simply pushed through 

 the surface, like the food, but its development 

 into the adult form has never been witnessed. While 

 in the parent's body it sometimes can scarcely be 

 distinguished from the food, which is often present 

 in large quantities, for the Amoeba has an insatiable 

 appetite, and crams itself with a heterogeneous col- 

 lection of microscopic organisms of various colours, 

 green, brown, red, &c. 



A creature of such low organization as that of 

 which we write, one would think, must be subject 

 to many accidents in the course of its life, and so it 

 is, but it seems to meet them all with indifference. 

 Does it become pierced with a hair, it travels about 

 impaled, apparently none the worse. Does its jelly- 

 like substance become squashed or divided, the re- 

 mains severally collect themselves into small pellets 

 and creep away each a perfect amoeba. By more 

 than one microscopist has it been seen to voluntarily 

 detach portions of its substance, which immediately 

 took their departure to begin life for themselves. 

 Another extraordinary fact, too, has been witnessed 

 with creatures very closely allied to this {Difflugia), 

 viz., two individuals have combined so closely as to 

 form but one globular mass, — one of the shells with 

 which these Rhizopods are severally invested being 

 empty, though attached by its mouth to the other, 

 in which the globular mass of sarcode lay. 



I remember, some short time ago, while looking 

 at a curious Rotifer% which I never saw before, seeing 

 an Amoeba caught up by the currents caused by the 

 ciliated disc, and alternately attracted to and dis- 

 charged from the centre of the tiny whirlpool many 

 times, till at last the animalcule swung itself round 

 in another direction (fig. 209), and the Amoeba, 

 apparently none the worse from the rough treat- 

 ment it had experienced, crept or rolled away on 

 its own business. 



According to the size and transparency of the 

 specimens, their activity, and the manner in which 

 they extend their pseudopodia, are they distinguished 

 by names. The utmost doubi, however, hangs on 



* Professor Williamson's paper on the Structure of the 

 Amoeba, in " Popular Science Review." 



t Some observers believe in the existence of a thin pellicle 

 enclosing the whole. 



% Obtained at Kcston, 18th December, 1865. 



