8 AMCEBA 



different Amoebae : sometimes there are granules of chroma- 

 tin in an achromatic ground substance (F) : sometimes the 

 chromatin is collected towards the surface or periphery of 

 the nucleus : sometimes, again, it becomes aggregated in the 

 centre (G, H). In the latter case the nucleus is seen to have 

 a deeply-stained central portion, which is then distinguished 

 as the nucleolus. 



When it is said that Amoebae sometimes have one kind of 

 nucleus and sometimes another, it must not be inferred that 

 the same animalcule varies in this respect. What is meant 

 is that there are found in stagnant water many kinds or 

 species of Amoeba which are distinguished from one 

 another, amongst other things, by the character of their 

 nuclei, just as the various species of Felis the cat, lion, 

 tiger, lynx, &c. are distinguished from one another, amongst 

 other things, by the colour and markings of their fur. 

 According to the method of binomial nomenclature intro- 

 duced into biology by Linnaeus, the same generic name 

 is applied to all such closely allied species, while each is 

 specially distinguished by a second or specific name of its 

 own. Thus under the genus Amoeba are included Amoeba 

 proteus (Fig. i, c, E, and F) with long lobed pseudopods and 

 a nucleus, containing evenly-disposed granules of chromatin ; 

 A. quarta (A and B), with short pseudopods and numerous 

 nuclei ; A. verrucosa (G and H) with crumpled or folded 

 surface, no well-marked pseudopods, and a nucleus with a 

 central aggregation of chromatin, or nucleolus ; and many 

 others. 



Besides the nucleus, there is another structure frequently 

 visible in the living Amoeba. This is a clear, rounded space 

 in the ectosarc (c, E, and G, c. vac], which periodically dis- 

 appears with a sudden contraction and then slowly re-appears, 

 its movements reminding one of the beating of a minute 



