Morphologie, etc. — Varietäten, etc. 99 



of the nucleus the cystode or pseudo-moneral stage has become a 

 true cell of the simplest type, t'or which the writer proposes the 

 terms protocyte. This is the starting point of an infinite series of 

 further complications and elaborations in many directions. The 

 most conspicuous of these modifications of cell-structure are those 

 affecting the periplasm, or, as now it may be termed, cytoplasm. 

 The nucleus remains comparatively uniform; it may indeed vary 

 infinitely in details of structure, but in principle it remains a con- 

 centralion or aggregation of numerous grains of chromatin. 



In the evolution of nuclear division by karyokinesis two distinct 

 processes are being developed and perfected in a parallel manner, 

 but more or less independently; first, the method of the partition 

 and distribution of the chromatingrains betvveen the two daughter- 

 nuclei; secondly, the mechanism whereby the actual division of the 

 nucleus and the Separation of the two daughter-nuclei are effected 

 in the cell-division. This process of nuclear division is in the 

 author's opinion , of enormous importance in the general evolution 

 of living organisms. 



One point of general interest in the evolution of the cell has 

 been treated in brief reference: the divergence of animal and vege- 

 table cells. It seems clearly indicated to the author that the typical 

 green plant-cell took origin amongst the Flagellata, in that some 

 members of this group of Protozoa acquired the peculiar chro- 

 matophores which enables them to abandon the holozoic or animal 

 mode of life in exchange for a vegetative mode of nutrilion by means 

 of chlorophyll-corpuscles. 



The crux of the authors scheme is the homology postulated 

 between the biococcus and the chromatinic particle — chromidio- 

 some or chromiole — of true cells. The author is not the originator 

 of this view, but supports it by setting forth the reasons which 

 have convinced him that the extraordinary powers and activities 

 exhibited by the chromatin in ordinary cells are such as can only 

 be explained on the hypothesis that the ultimate chromatinic units 

 are to be regarded as independent living beings, as much so as the 

 cells composing the bodies of multicellular organisms. 



For further detail the very rieh paper must be read in original. 



M. J. Sirks (Bunnik). 



Davenport, C. B., The form of evolutionary theory that 

 modern genetical research seems to favor. (American 

 Naturalist. L. p. 449—465. 1916.) 



The writer summarizes the contents of his paper in these words: 

 A theory of evolution that assumes internal changes chiefly 

 independent of external conditions, i. e., spontaneously arising, and 

 which proceeds chiefly by a Splitting up of and loss of genes from 

 a primitiveli^^ complex molecular condition of the germ plasm seems 

 best to meet the present State of our knowledge. 



Such a theory receives support from various fields. 



1. From ontogeny, where the differentiated end stage is derived 

 from a relatively undifferentiated, but probably molecularly com- 

 plex egg. 



2. From paleontology, where the history of the phylum seems 

 governed by internal laws. 



3. From experimental breeding where progress is afforded only 

 as internal changes permit. 



