302 



NA TURE 



{Jan. 27, ^887 



might almost be foreseen : Berthold proposes to recast 

 the definition of protoplasm, and to subordinate to it — 

 the fluid mixture absent from no living cell — cytoplasm, 

 nucleus, chlorophyll-bodies, vacuoles, tannin and oil- 

 drops, &c., as so many'parts, of the protoplasm as a whole. 

 He urges that the introduction of the ideas cytoplasm, 

 ectoplasm, and so on, have driven the time-honoured 

 word protoplasm out of the field, whereas its usefulness 

 as a comprehensive word -though with a somewhat 

 different meaning from the current one — for the whole is 

 undoubted. Moreover, it is to be insisted upon that the 

 protoplasm is active as a whole. 



The discussion as to the meaning of the term " organ- 

 ised " must be here passed over, with many other points 

 of interest. 



In the third chapter we have a long analysis of the 

 movements of naked masses of protoplasm. All turns 

 upon the tendency of a mass of protoplasm to assume the 

 form of a spherical drop ; this can only be due to the 

 same causes which impel a drop of any accepted liquid to 

 assume the drop condition. Justice could not be done 

 by summarising this analysis, and the demonstration that 

 cylinders of protoplasm, like cylinders of liquids, tend to 

 break up in a definite way. The end result of a long 

 argument is, that the amosboid condition depends upon 

 the degree of wetting of the environment by the fluid 

 protoplasm and vice vc?-sd. 



If three fluids which do not mix are in contact with 

 one another, the tensions at their surfaces can be mathe- 

 matically investigated, and Berthold maintains that the 

 principles here concerned govern the behaviour of a drop 

 of protoplasm as they do that of an ordinary liquid under 

 the given conditions. The phenomena of spreading out, 

 putting forth and withdrawing pseudopodia, rounding off, 

 &c., are due to the same causes and ruled by the same 

 laws as the flowing of one liquid over another, or its with- 

 drawal from it (glycerine and alcohol e.g.), or its assump- 

 tion of the drop form, and so on. Of course amoeboid 

 movements are complex, because the liquid amceba is not 

 a simple fluid, but is undergoing rapid changes due to its 

 metabolism and exchanges with the environment, pro- 

 cesses which are acting with different energy at different 

 places. It must be clearly understood that a rapid 

 survey of Berthold's position cannot do justice to his 

 argument : whether his position is accepted or rejected, 

 there is no doubt that he clearly sees and provides 

 for many important difficulties, some of which seem to 

 have been overlooked. It will be regarded as a startling 

 idea by some (though the idea is not altogether new) that 

 fine pseudopodia are not the results of activity on the 

 part of the amoeba : such pseudopodia must be looked 

 upon as dnnti?i out by the surrounding medium, not put 

 out into it. Here, again, exceptions occur where blunt 

 processes are driven forth by local contractions and 

 other causes, but the sum total of all the argument is 

 (as expressly stated again on p. 109) that the amoeboid 

 condition is the symptom that the organism wets the 

 substratum and displaces the surrounding medium, indi- 

 cating , that the intensity of the tension between the 

 medium and the protoplasm is but small. The discussion 

 as to the causes and effects of the internal movements in 

 protoplasm must here be passed over, with the simple 

 remark that the author sees no difficulty which cannot be 

 explained from our knowledge of the mechanics of liquids. 

 On p. io5 is proposed an explanation of the remarkable 

 filaments observed by F. Darwin on Dipsacus sylvestris. 



Chapter IV. deals with what is practically a continua- 

 tion of the second chapter— the symmetry or arrangement 

 of the cell-contents. The stratified or shell arrangement 

 is again expressly referred to, and an attempt made to 

 explain it on the main assumption of the book. The 

 arrangement referred to is a consequence of e.xchanges 

 (diff'usion, absorption, &c.) with the environment : passive 

 particles suspended in the cell would have to assume 



positions which are definite ; active particles {i.e. particles 

 which themselves exchange with the layer in wh.ch they 

 are embedded) might interfere with the simple shell 

 arrangement, and we have systems within a system. 

 After examining what occurs in the case of a spherical 

 system or cell, the author extends the analvsis to an 

 ellipsoid and other anisodiametric systems, and finds the 

 results accord with what is found in Nature. The ques- 

 tion of the " Hautschicht " is then attacked, and De 

 Vries' late statements as to the existence of a pellicle or 

 " wall " around the vacuole are criticised. Berthold, to 

 put it shortly, condemns this pellicle as an artificial pro- 

 duct — a " precipitation-membrane " — in many if not in 

 most cases. On p. 154 it is still more emphatically stated 

 that the cell-wall inside the cell is formed " always in the 

 interior of the protoplasm, never on its surface," and it is 

 probable '' that the same is the case even when free 

 masses of protoplasm surround themselves with a mem- 

 brane." The membrane stated to exist around the 

 nucleus is condemned, with a certain reserve, as a pro- 

 bable precipitation-membrane. Other interesting points 

 must be passed over. 



The fifth chapter is practically concerned with showing 

 that in spite of the great variety of forms exhibited by the 

 chlorophyll-bodies of different plants, especially Alga;, 

 their position, consistence, changes in form, division, &c., 

 can be explained in accordance with the view that they 

 are parts of an emulsion. Other cell-contents are con- 

 sidered also — oil-drops, tannin, nucleus, vacuoles, &c. — 

 but at less length. The chlorophyll-corpuscles of higher 

 plants are compared to drops resting on a substratum 

 which they do not wet, their shape being in part due to 

 radial pressures. When they are more extended and 

 amoeboid, their actions are explained according to the 

 principles (contact of three surfaces, &c.) employed before. 

 Spirogyra and other Conjugate present difficulties. 

 While the " chlorophyll-apparatus " displays a relatively 

 large surface, the converse is the case with nuclei and 

 other cell-contents, and the form of the spherical drop 

 (maximum cubic contents with minimum superficial area) 

 is usual ; though exceptions exist and are investigated. 



The division of chlorophyll corpuscles is then examined, 

 and this leads naturally to the division of the nucleus and 

 cell, which is treated separately. A spherical mass of 

 fluid must increase its surface if it divides : this implies 

 a diminution of tension at the common surface (as with 

 the formation of pseudopodia), and concentric shells in 

 the medium or in the mass of fluid in question. All the 

 conditions fulfilled, pseudopodia can be formed either 

 from the medium into the mass, or from the mass into the 

 medium. An annular pseudopodium would divide the 

 spherical (or spheroidal) mass into two. This is, shortly 

 put, the position as Berthold views it. He then again 

 applies the analysis of dividing cylinders, and proceeds 

 to apply the results to what is observed in a cell. The 

 radial pressure, and growth in one direction of the cell, 

 may be important factors. But the real difficulty is met 

 with when considering the division of spherical bodies in 

 the cells of the growing-points, for instance ; and the 

 same applies to cell-division. Why should a sphere — a 

 stable form — pass over into an elongated body, which 

 then divides? It must be assumed that " under the in- 

 fluence of its own metabolism, and that of its environment 

 a bi-polar symmetry arises in the chlorophyll-corpuscle, 

 in consequence of which the division takes place equa- 

 torially.'' 



This leads to the sixth chapter, which is in many, 

 respects the most important, as it is the most interesting. 

 After reviewing the process of cell-division generally, the 

 author separates the essential from the unessential pro- 

 cesses, and agrees with Strasburger that the division of 

 the nucleus must be regarded as an accompanying 

 phenomenon. The division of the ovum of Echinus and 

 Cioiia is described ; soon after the male and female 



