CHAPTERS ON EVOLUTION. 



non for the manifestation of life and vital action, let us examine a 

 few of the aspects in which this substance makes its appearance as. 

 the medium for the exhibition of living actions. It is by no means- 

 unusual to find that familiarity with a name in the abstract implies a 

 total inability to appreciate the concrete aspects of the substance 

 which the name describes. Despite the wide acceptation of the name 

 "protoplasm," it is matter of common observation that the nature of 

 the substance itself, as well as its qualities and traits, are frequently 

 unknown by those to whom the term is as a " household word." As a 

 preliminary study, then, the discussion of protoplasm itself, and its, 

 varied phases, will not be without its value in the determination of its 

 importance as "the physical basis of life." What protoplasm is, 

 chemically and physically, may be very briefly and readily de- 

 scribed. Chemically, it stands as the type of a class of compounds 

 to which Mulder gave the name of "proteine" substances. Of 

 such substances, common albumen seen in white of egg is a familiar 

 example ; and white of egg, indeed, hardly differs, save in minute 

 chemical particulars, from protoplasm itself. The latter substance is 

 resolvable by chemical analysis into the elements carbon, hydrogen, 

 oxygen, and nitrogen, along with mere traces of sulphur and phos- 

 phorus. Physically, protoplasm presents itself as a clear, viscid, 

 and semi-fluid substance, often highly granular from the presence 

 within its substance of fatty or other particles. By immersion in a 

 carmine solution, dead protoplasm may be stained deeply, whilst 

 living protoplasm resists all such contact with colour ; and when we 

 have added that protoplasm can be made to contract under electrical 

 stimulus, and that it coagulates at from 40 to 50 Cent, we shall 

 have completed our examination of its readily observed properties. 



Let us now turn to consider some of its living aspects and 

 characters. The low-life deeps which it is the province of the micro- 

 scope to explore, present us with a suitable starting-point for our 



inquiries ; and the 

 stagnant pool, or 

 decomposing infu- 

 sion, may be made to 

 render from their un- 

 savoury depths the 

 means for scientific 

 sweetness and light. 

 Wandering, in its 

 own erratic fashion, 

 ever in search of 

 fields and pastures new, stumbling over the fragments of weed 

 that lie in its miniature path, and presenting us with a substance 

 which may be paradoxically described as exhibiting every con- 



FIG. 20. AMCEBA. 



