98 Biologie. — Morphologie, Teratologie, etc. 



so starke Streckung der Blüte verursachen, dass diese Deckblätter 

 gesprengt werden. M. J. Sirks (Bunnik). 



Minchin, E. A., The evolution ofthecell. (American Natu- 

 ralist. L. p. 1—38, 106-118, 271—283. 1916.) 



The writer proposes in this paper, to deal with an aspect of 

 cytology which appears to him not to have received as yet the 

 attention which it deserves, namely the evolution of the cell itself 

 and of its complex Organization as revealed by the investigation of 

 cytologists. The type of cell has a long history of evolution behind 

 it, the author defines ciearly the sense in which he proposes to 

 use certain terms, more especially the words cell, nucleus, chro- 

 matin, protoplasm and cytoplasm. 



Chromatin-elements are regarded as the primary and essential 

 constituents of living organisms and as representing that part of a 

 living body of any kind which can be foUowed by the imagination, 

 in the reverse direction of the propagative series, back to the very 

 starting-point of the evolution of living beings. This assumption is 

 founded upon this argument: the chromatine constituents of the 

 cell contrast with all the other constituents in at least three points: 

 physiological predominance, especially in constructive metabolism; 

 specific individualization; and permanence in the sense of potential 

 biological immortality. For the hypothetical primitive organisms 

 Mereschko wsky's term biococci is used. They must have been 

 free-living organisms capable of building up their living bodies by 

 synthesis of simplest chemical produits. 



From these primitive biococcal type the evolution of living 

 things must have diverged in at least two principal directions. Two 

 new types of organisms arose, one of which continued to specialize 

 further in the vegetative mode of life, while the other type develo- 

 ped an entirely new habit of life, namely a predatory existence. 

 The vegetative type gave rise to the bacterial form of organism; 

 as simplest representative Micrococcus is mentioned, from which 

 an infinity of forms arises by processes of divergent evolution and 

 adaptation. The evolution of the bacterial type of cell is not fol- 

 lowed further. 



In the predatory tj^pe of organism, the first step in evolution 

 has been the formation round the biococci of an enveloping matrix 

 of protoplasm for which the term periplasm (Lankester) is most 

 suitable. The final result of these changes was a new type of orga- 

 nism which, compared with the original biococci was of considerable 

 size, and consisted of a droplet of alveolar, amoeboid periplasm in 

 which were imbedded a number of biococci. In this manner a stage 

 of evolution has been reached which the author proposes to call 

 the pseudo-moneral or cytodal stage, since the place of these orga- 

 nisms in the general evolution of life corresponds very nearly to 

 Haeckel's conception of the Monera as a stage in the evolution 

 of organisms, though not at all to his notions with regard to their 

 composition and structure. The bodies of these organisms consisted 

 of a periplasm corresponding to the cytoplasm of the cell, contai- 

 ning a number of biococci or chromatine-grains. 



The next stage of evolution was the Organization of the chro- 

 matin grains (biococci) into a definite cell-nucleus. This is a process 

 which can be observed actually taking place in many Protozoa in 

 which "secondarv" nuclei arise from chromidia. With the formation 



