446 TRANSACTIONS OF SECTION D. 



existence during the life-liistory of the organism. Both these methods, which 

 are founded mainly on observation, require to be checked and controlled by 

 the experimental methods of investigating both the functions and behaviour 

 of the organism and of its parts. 



So long as cytologists limit their studies to the cells building up the tissues 

 of the higher animals and plants, the comparative method has a correspondingly 

 limited scope, and that of the ontogenetic method is even more restricted. 

 Both methods receive at once, however, an enormously extended range when 

 the Protista are taken into consideration. Then, moreover, we see the dawning 

 possibility of another method of investigation, that, namely, of the chemical 

 evolution of the organisms. Already some of the simpler Protista, the 

 Bacteria, are characterised and classified largely by their chemical activities ; 

 but in more complex organisms, in those which have attained complete cell- 

 structure, such as Protozoa, the data of chemistry do not as yet supply the 

 evolutionist with a helpful method of investigation. 



The problem of cell-evolution may be attacked by the help of the methods 

 outlined in the foregoing remarks, beginning with the consideration of the 

 primary structural differentiation of the typical cell, the distinction of nucleus, 

 or rather chromatin, and cytoplasm. Since all cells known to us exhibit this 

 differentiation, we have three possibilities as regards the manner in which it 

 has come about, which may be summarised briefly as follows : either the 

 cytoplasmic and thromatinic constituents of the cell have arisen as diffei-entiations 

 of some primitive substance, ■which was neither the one nor the other; or one 

 of these two substances is a derivative of the other, in the course of evolution, 

 cither cytoplasm of chromatin, or chromatin of cytoplasm. 



The idea of a primitive, inidifferentiated protoplasmic substance was first 

 ]5ut forward by Haeckel, who employed for it the term ' plasson ' invented 

 by Van Beneden ' to denote ' la substance constitutive du corps des Moneres et 

 des cytodes ... la substance formative par excellence.' The simplest ele- 

 mentary organisms were not cells, but cytodes, ' living independent beings 

 which consist entirely of a particle of plasson ; their quite homogeneous or 

 uniform body con.'^ists of an albuminous substance which is not yet differenti- 

 ated into karyoplasm and cytoplasm, but possesses the properties of both 

 (ombined.''° It is empha.si.sed n that a sharp distinction must be drawn 

 between protoplasm and plasson, the latter being a homogeneous albuminous 

 formative substance (' Bildungsstoff ') corresponding to the ' Urschleim ' of 

 the older Nature-philosophy. 



Haeckel, as was usual with him, did not content himself with putting 

 forward his ideas as abstract speculations, but sought to provide them with a 

 concrete and objective foundation by professing to have discovered, and 

 describing in detail, living and existing organisms which were stated to remain 

 permanently in the condition of cytodes. In consequence, a purely speculative 

 notion was permitted to masquerade for many years under the false appear- 

 ance of an objective phenomenon of Nature, until the error was discovered 

 gradually and the phantom bani.^hed from the accepted and established data 

 of biology. Organisms supposed to be of the nature of cytodes constituted 

 Haeckel's .systematic division Monera, of which there were supposed to be two 

 subdivisions, tlie Phytomonera and the Zoomonera. The Phytomonera were 

 stated to have the plasson coloured green and to live in a plant-like manner ; 

 the Zoomonera were colourless amoeboid masses of plasson which nourished 

 '.hemselves in the animal manner. The Bacteria were also included by Haeckel 

 in Ills ^Monera, apparently, or at all events ranked as cytodes. '= Most import- 

 ance, however, was attributed by Haeckel to the large amoeboid forms of Monera, 

 described as without nuclei of contractile vacuoles, but as representing simply 

 structureless contractile masses of albumin ('Eiweiss'), perfectly homo- 

 geneous;'^ examples of these were announced to exist under the names 

 ' Protamceba ' and ' Protogenes,' denoting forms of life which Haeckel claimed 



^ Bull. (Ic I'Aidd. 'Hail, tie Bih/itjue, second series, vol. xxxi. (1871), p. 346. 

 '" AiUhropaiiciiir. sixth edition, Leipzig, 1910, p. 119. 

 " Jliid. p. ,5.32. 

 "= Ibid. p. 119. 

 " See his Prinzipicn der gonerellen Morphologie, Berlin, 1906, p. 61. 



