Jan. 27, 1887] 



NA rURE 



301 



The itle of the book must be taken in a comprehensive 

 sense, br the whole " cell-theory " (if we possess one) is 

 under review in the nine chapters into which the text is 

 divided. This extensive aim is justified by the author's 

 treatment of the subject, which affords an admirable 

 survey of current botanical speculation. 



Before proceeding to a closer examination of the work, 

 we may state that there are seven well-executed plates, 

 with descriptions which are too short. The index might 

 have been more ample — it includes the names of plants 

 and authors only — but the table of contents is very full 

 and good. 



An introduction of eleven pages leads us at once to the 

 chief position assumed by the author. So long as we do 

 not understand the Aiiiaiht, we must be in the dark as 

 regards the mechanism of life in higher organisms. No- 

 thing has been gained by regarding protoplasm as " living 

 proteid," or as containing " living " as opposed to "dead" 

 proteids, and so forth ; moreover, no clearness, but rather 

 the contrary, has so far resulted from hypotheses as to 

 the "structure'' of protoplasm, or from distinctions be- 

 tween " idioplasm " and other constituents. The author 

 therefore inquired whether we are not perhaps treading 

 an aimless path, and whether we should not go back and 

 examine earlier views, and proceed anew. The conse- 

 quence to his mind was the resumption of the old analogy 

 between a drop of protoplasm and a drop of fluid, and 

 he was led to inquire into the analogy more deeply, 

 especially on finding that a detailed analysis of the 

 problem had not before been seriously undertaken. As 

 the general result of investigations begun in 18S2, the 

 author decides that protoplasm is to be regarded as a 

 highly complex emulsion, differing in consistence in the 

 different cases. There is nothing in the cheiiiistry and 

 metabolism known which need clash with this view of the 

 fluid nature of the " physical basis of life," and the author 

 decides that the forces upon which the changes of form, 

 internal movements, and so forth, depend, are the same 

 as those which determine whether a fluid shall assume 

 the form of a drop, or drops, or spread out and wet 

 another body, and so on — in fact, the forces concerned in 

 surface-tensions. 



The author frankly admits the difficulty, and even seem- 

 ing impossibility, of imitating some of the conditions, or 

 even of deciding whether the actions of protoplasm accord 

 with the theory. This must naturally be the case ; and of 

 course no one expects him to imitate all the conditions ex- 

 perimentally. The method employed is essentially deduc- 

 tive and analytic throughout, and for this reason the 

 greatest possible care must be employed in taking any 

 step forward. Partly on this account, and partly owing 

 to other circumstances, the book needs cautious reading, 

 and great difficulties will be felt in regard to many points. 

 This is apart from an undoubted (though perhaps unavoid- 

 able) blemish in the book, which consists in the author 

 so often putting off for some pages the consideration of a 

 subject commenced. 



The key-note, as it were, of the work having been in- 

 dicated, a few words must be said regarding some leading 

 features in the various chapters. The first subject dealt 

 with is the layered or stratified nature of the typical cell. 

 A spore of Eqiiisctttm, for instance, may be regarded as 

 a system of concentric layers. First there is a central 

 nucleus : then various layers of protoplasm, of which 

 the innermost is colourless and contains certain minute 

 granules, the second is thicker and carries the chlorophyll- 

 corpuscles, the third is hyaline and contains lenticular 

 refractive bodies of peculiar nature ; then follows the cell- 

 wall, if nothing further. The cell-wall is usually com- 

 posed of three or more layers. 



If we consider the cells of a tissue, Rerthold points out 

 that a given partition membrane must be regarded as 

 dividing and belonging to two symmetrical plasmatic 

 systems, and as being their middle and innermost layer. 



But all cells are not systems of concentric layers. Not 

 only are excentric layers found, but a complexity is intro- 

 duced as soon as the sap-vacuoles appear, in many cases 

 making the cell not monocentric but polycentric. The 

 normal order of the layers, as exemplified by the spore of 

 Eqiiisetum, or any simple cell with one large vacuole, 

 &c., may be distinguished from the inverse order ex- 

 hibited, for instance, by the cords in a Caulerpa, or the 

 central mass in a cell containing raphides, or anywhere 

 where the sap bathes the system of layers referred to. 



It is then shown that in many cases where oil-drops, &c., 

 have usually been regarded as lying free in a cell, they are 

 inclosed in an ingrowth from the cell-wall, reminding us 

 of cystoliths. An examination of intercellular spaces 

 follows : the most interesting question is as to the exist- 

 ence of protoplasm in lacunae between cells. Berthold 

 quotes Aciinitum Napcllus as affording conclusive evi- 

 dence, and confutes the contention of Gardiner and 

 Schenck against Russovv's statements. Berthold goes 

 much further, however. He finds a thin layer of proto- 

 plasm overlying the cuticle of the epidermis and of spores, 

 and, to put it shortly, concludes that the cell-wall -is 

 formed and embedded in protoplasm, and not excreted on 

 its surface — the cell-wall is a supporting apparatus, not a 

 protective one. Again, a cell forming part of a tissue 

 cannot be forthwith compared with a unicellular Alga, 

 for this reason : the latter may be regarded as consisting 

 of two parts, (i) the inner protoplasmic system with its 

 contiguous share of cell-wall, (2) the outer strata of cell- 

 wall plus the hypothetical covering of protoplasm. Only 

 the first of these two parts of the algal cell can be com- 

 pared with a tissue-cell. 



The relation of these ideas to Sachs's view, that we are 

 to regard a plant as a whole cut up into cell-chambers, 

 and not as a whole built up of single cells, is obvious to 

 all who have followed recent speculations in botany. 



It is, of course, impossible to go at any length into the 

 contents of all the chapters. The second is concerned 

 with the finer structure of the cell— nucleus, chlorophyll- 

 corpuscles, and other cell-contents. Incidentally we may 

 note the einphatic statement that starch is Jiot formed in 

 the Mclanophyccce {■^. 57); that the word "microsome" 

 has no definite meaning, and had better be discarded 

 (p. 61). Later on the author expressly states his inability 

 to confirm Strasburger's and Schmitz's conclusions that 

 microsomes are enplojed in building up the cell-wall 

 (p. 208), and even hints at confusion between crystalline 

 particles and microsomes in the case oi Spirogyra : 



If protoplasm is an emulsion, it follows that the 

 various processes of separation of sap-vacuoles, oil- 

 drops, crystalline and other particles, have to be ex- 

 plained as according with similar separations m lifeless 

 mixtures. Berthold finds no difficulties insuperable here, 

 and even discusses the probable origin and disappearance 

 of chlorophyll-corpuscles and nuclei on the assumption 

 that they are part of the protoplasm. Although they 

 now always arise by the division of those previously 

 existing, they must have been formed from protoplasm in 

 the first instance. The action of external stimuli offers a 

 fertile subject for discussion. As regards geotropism, 

 the author regards "the primary effect of gravitation " 

 as consisting in the different rates of movement of sub- 

 stances of different specific gravity. 



The supposition that anything is explained by regard- 

 ing protoplasm as essentially " living proteid," is severely 

 criticised on pp. 74 and 75, and the author agrees with 

 Baumann that the arguments which exalt proteids into 

 the position of being the most essential constituent of 

 protoplasm would apply equally v/ell to water. The 

 " living substance of organisms" is always an extremely 

 complex mixture. At the same time, it would seem that the 

 author here raises some gratuitous difficulties, since no 

 biologist really regards protoplasm as a simple substance, 

 proteid or otherwise. One consequence of the discussion 



