THE CELL AND PROTOPLASM 



tural framework of the cell wall is ever 

 composed of any randomly oriented chain- 

 molecules. 



Complementing these three papers on 

 ''The Cell and Protoplasm" are the two 

 that follow on "The Cell and Chromo- 

 somes." The first of these is by Jennings 

 on "Chromosomes and Cytoplasm in Pro- 

 tozoa" and the second by Goldschmidt on 

 "Genes and Chromosomes." 



The well-known nuclear cycle that recurs 

 with each cell division during the ontogeny 

 of a multicellular organism is cited by 

 Jennings as crucial evidence of material 

 exchanges between the nucleus and the 

 cytoplasm. Accordingly, each condensed 

 chromosome enlarges during the later 

 phases of mitosis to become vesicular, from 

 material taken up from the cytoplasm. 

 Within the resulting contiguous chromo- 

 some vesicles which constitute the reformed 

 nucleus, the newly acquired cytoplasmic 

 material is altered and, as such, is returned 

 again to the surrounding cytoplasm upon 

 the subsequent breakdown of the vesicular 

 wall of each chromosome, whose residue 

 again condenses for the following mitosis. 

 These cyclic interchanges and transforma- 

 tions apparently provide the essential 

 mechanisms of cellular differentiations 

 both in the ontogeny of multicellular or- 

 ganisms and in the racial variations of 

 unicellular organisms. As illustrative of 

 the latter, De Garis' recent results from 

 crossing large and small races of Parame- 

 cium are discussed. These results show 

 that the ex-con jugants having unlike cyto- 

 plasms but like nuclei retain their size dif- 

 ferences for about 22 generations, where- 

 upon these differences gradually disappear. 

 Evidently, therefore, the two different cy- 

 toplasms are finally transformed by the 

 like nuclei so that the two races of unequal 

 size come to have the same size. 



By what mechanism of the nucleus the 

 cyclic modifications, and so racial differ- 

 ences, may be effected is discussed in the 

 succeeding paper by Goldschmidt. His 

 thesis tends to discount the commonly ac- 

 cepted gene theory of Mendelian heredity 

 and proposes instead a chromosome theory 

 in which the occurrence of genes as discrete 



entities, arranged bead-like in a definite 

 order, need not be assumed. From the 

 similarities in chromosome form and struc- 

 ture in the cells of all organisms, wherein a 

 visible fibril-like core may represent a 

 single protein unit of definite stoichiomet- 

 ric properties along its axis, it would be 

 more in accord with recent X-ray, chem- 

 ical, and polarimetric analyses to identify 

 the chromosome as a chemical unit. Such 

 a unit might show any amount of differ- 

 ential chemical complexity in different 

 chain molecules of similar length. This 

 concept would ascribe to the chromosome a 

 linear pattern and would account for mu- 

 tational changes (the Bar-effect, mosaicism, 

 position-effect, etc.) as due to changes in 

 the chromosomal pattern (inversions, 

 translocations, duplication of parts, etc.) 

 rather than to changes within discrete par- 

 ticles, or genes, of molecular order. 



The demonstrable interrelations between 

 cytoplasm and nucleus which would ac- 

 count for differentiation in both the indi- 

 vidual and the race obviously represent 

 but one of the two major components in the 

 fundamental phenomena of living things. 

 The other essential component is, of course, 

 the environment. The role of environmen- 

 tal factors is well exemplified in the three 

 papers that follow on developmental as- 

 pects of the cell and its relation to the or- 

 ganism. These include "Cellular Differ- 

 entiation and External Environment" by 

 Child, "Cellular Differentiation and Inter- 

 nal Environment" by Harrison, and "Cell 

 and Organism" by Kofoid. 



The external environment of the primor- 

 dial cell, according to Child, is a determin- 

 ing factor in its differentiation at the very 

 onset of develcpment. The cell's primor- 

 dial pattern is essentially a surface-interior 

 pattern which reflects an intimate relation- 

 ship with its environment. Also, by action 

 of a suitable differential in its external en- 

 vironment, its polar or axiate differentia- 

 tion is duly determined. Any one or more 

 of various environmental differentials may 

 induce this superimposed axiate pattern, 

 as demonstrated in numerous experiments 

 by Child and by others. Accordingly, the 

 axiate pattern arises as a gradient which is 



