CHEMISTRY OF THE PROTOPLAST 61 



or may not be enclosed by a cell-wall. The cellular segments of Cladophora, 

 Cham, &c., are therefore coenocytes, and Codium, Neomeris^ Caulerpa, &c., 

 apparently represent less highly specialized evolutionary developments in the same 

 direction, while the body of a typical Myxomycete corresponds to a single coeno- 

 cytic cell, in the Acrasiae the fusion of the constituent protoplasts being an 

 imperfect one. In such a plant as Neomeris dumeiosa each of the rudimentary 

 cell segments, into which the plant is divided, retains its own chloroplastids, nuclei, 

 and the bulk of the plasma, and the same applies to other Siphoneae as well, so that 

 these organisms can no more be regarded as unicellular than a row of sieve-tubes, 

 and indeed a phanerogamic tree, in so far as protoplasmic connexions exist between 

 its component protoplasts, might with equal justice be regarded as a single cell. 

 Moreover, if it is admitted that the reproductive organs form an essential part of 

 the entire plant, then Mi/cor, Vattcheria, JVeomeris, &c., all when adult become 

 multicellular, for, using the term in its most restricted sense, only those organisms 

 are unicellular which are composed of a single protoplast. The usually accepted 

 distinction between uni- and multicellular plants is an artificial one, and since it was 

 originally founded on a misconception, no importance need now be attached to 

 it. Ed.] 



SECTION n. Chemistry of the Protoplast. 



As its structure indicates, the protoplast is a physiological but not 

 a chemical entity, for even if all the substances of which it is composed 

 could be mixed together in the right proportions, we should still fail 

 to create a new living protoplast. Indeed, the life of the protoplast, as 

 well as that of the smallest organ it contains, is destroyed by triturition, 

 and even the smallest physiological units are not unorganized chemical 

 compounds, but are organized bodies having a definite structure. 



The most complete chemical knowledge of the substances composing 

 the protoplast (Sect, i) is as little able to make us understand the nature 

 of the living organism, as a knowledge of the chemistry of iron and coal 

 is to enable us to comprehend the mechanism of the steam-engine and the 

 printing-press, if we are unacquainted with them. Nevertheless, a thorough 

 knowledge of the chemistry of the protoplast forms an essential pre- 

 liminary to all studies upon the nature of the vital mechanism. Indeed, 

 it is hardly possible to over-estimate the physiological importance of 

 a complete knowledge of the chemical nature and properties of the 

 different proteid substances. 



Chemical affinities and chemical quality play a more important and 

 complicated role in an organism than in a machine. It is by chemical 

 changes in the protoplast itself that building material is formed, and the 

 necessary energy rendered available ; while nourishment, growth, and move- 

 ment are all directly or indirectly dependent upon chemical affinities and 

 properties, to which also the retention of the same general composition 



