CELL AND ORGANISM 



By CHARLES A. KOFOID 



DEPARTMENT OF ZOOLOGY, UNIVERSITY OF CALIFORNIA, BERKELEY, CALIF. 



In the score of years following the pub- 

 lication of Charles Darwin's Origin of Spe- 

 cies, in 1859, two new lines of biological in- 

 vestigation profoundly influenced biolog- 

 ical thinking and brought the Cell Theory 

 in line with the concept of the evolution of 

 plant and animal types, especially the 

 latter. 



The first of these was the increased at- 

 tention paid to the development of marine 

 animals, which brought under inspection 

 all of the invertebrate phyla. This resulted 

 in observations on the earliest stages of de- 

 velopment of the individual and clarified 

 the ontogeny of species belonging to many 

 phyla and classes on the basis of their cellu- 

 lar structure. Proponents of organic evo- 

 lution were quick to grasp the significance 

 of these findings which reenf orced the germ 

 layer theory. It also gave evidence of the 

 widespread prevalence of morula, blastula, 

 and gastrula stages amidst a diversity of 

 types of cleavage. The evolutionary sig- 

 nificance of these similarities was formu- 

 lated in Haeckel's Gastraea Theory which 

 predicated the universality of these em- 

 bryonic stages in all phyla, classes, and, 

 indeed, species. It thus laid the foundation 

 for what may be called, for the purposes of 

 this discussion, the embryonic theory of the 

 evolution of the metazoan organisms. 

 Added force was given to this view by 

 Haeckel's further step in his modification 

 of Von Baer's law into his Biogenetic Law 

 that ontogeny repeats phylogeny. Herbert 

 Spencer's concept of evolution as a process 

 of change from homogeneity to heteroge- 

 neity still further popularized the concept 

 of the simplicity of primitive forms of life 

 and of differentiation among similar simple 

 cells of the organism as the normal path of 

 evolution of organisms. 



Assistance rendered by the personnel of Works 

 Project Administration Official Project No. 65-1- 

 08-113, Unit CI, is acknowledged. 



The second line of investigation was the 

 use of imbedding and sectioning of verte- 

 brate embryos which confirmed and ex- 

 tended the observations of the development 

 of living forms observed by marine zoolo- 

 gists. It made feasible and placed on a 

 firm foundation the extension of the Germ 

 Layer Theory and the Gastraea Theory to 

 the yolk-laden eggs of fishes, reptiles, and 

 birds and to the highly modified eggs of 

 mammals. It also expanded and verified 

 the relatively great simplicity and early 

 similarities of the component cells of the 

 metazoan embryo. The general effect of 

 these findings was to establish the view that 

 the metazoan body was formed as a colony 

 of similar cells which later by histogenesis 

 became differentiated, instead of emphasiz- 

 ing that it was a single organism composed 

 of cells in interacting relations from the 

 beginning. 



The early history of the discovery of cells 

 has also inadvertently lent itself to the idea 

 of the individuality, separateness, and in- 

 dependence of cells. The very word cell in 

 itself is based on this idea. It savors of the 

 medieval segregation of the monastic life 

 and of the solitary confinement of prison 

 walls. As a matter of fact, when the En- 

 glish physicist and engineer, Robert Hooke, 

 sectioned and illustrated the polyhedrons 

 of elder pith and designated them as cel- 

 lula, he was in truth merely viewing the 

 secreted walls of cellulose and lignin of 

 vegetable cells. This picture of the cell is as 

 far from the facts presented by Schleiden 

 and Schwann in their cell theory as dark 

 from daylight, but the name attached to 

 this unit of organization of living bodies 

 has held its place with an extraordinary 

 tenacity, doubtless because of its very uni- 

 tary basic significance. It has, however, 

 brought with it certain sequelae which dis- 

 tort the relations of cell and organism. 

 Thus we find the words, syncytium, for 



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