590 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



classes of animals than in the higher ones. There are indications that an 

 evolution in the organismal differentials has occurred independently of each 

 other in plants as well as in animals. 



However, while in higher animals there has developed concomitantly with 

 the refinement of the organismal differentials a very pronounced integration 

 of the various organ systems into one connected, finely balanced mechanism, 

 in plants so marked a degree of integration has not taken place. The individual 

 parts of a higher plant remain much more independent of one another than 

 the parts of a highly differentiated animal. Inasmuch as in the case of animals 

 a certain parallelism exists between the differentiation of organs and tissues 

 and their integration into a whole organism, on the one hand, and the differ- 

 entiation and specialization of the organismal differentials, on the other, the 

 question may be raised whether, correspondingly, the organismal differentials 

 are less finely developed in plants and whether the latter possess individu- 

 ality differentials. The readiness with which grafting between two organisms 

 can be carried out in plants seems to indicate that individuality differentials 

 do not play a significant role. If they do exist, then a greater resistance of the 

 grafts to strange organismal differentials or a less strong reaction of the 

 host against the transplant covers up these finer differentials. But, there is 

 reason for assuming that in the course of evolution not only the mechanisms, 

 which make possible the manifestations of the finer differentials, undergo a 

 gradual development, but also that the substances, which serve as differentials, 

 undergo a corresponding evolution. Thus, Steinecke found that antigens 

 obtained from more primitive plants, when injected into rabbits for the pro- 

 duction of precipitins, are less differentiated than are those obtained from 

 higher plants. Accordingly, large group reactions predominate in algae; like- 

 wise, in cryptogamous plants the differences in the constitution of the proteins 

 between larger groups of plants are, as yet, slight. In phanerogamous plants 

 on the other hand, the specificity in the character of the proteins, as manifested 

 in the precipitin reactions, is greater. It may therefore be concluded that in 

 lower organisms in plants, we have to deal not merely with less finely 

 developed reactions against antigens or organismal differentials in general, 

 but also with less well developed and differentiated organismal differentials 

 and antigens. We may assume that the same conclusion applies to animals 

 and that here, also, there is a parallelism not only between phylogenetic 

 evolution and the fineness of reactions against organisms, but also between 

 phylogenetic evolution and the development of organismal differentials and 

 the corresponding antigens. 



As to the chemical substratum in which the changes take place, which paral- 

 lel the structural and functional evolution, there is justification for believing 

 that proteins, either as such or in combination with other groups, play the most 

 prominent role ; and it may furthermore be held that the phylogenetic evolution 

 of the organismal differentials was associated with an increasing complexity 

 of protein substances. However, our knowledge as to such evolutionary changes 

 in the proteins is as yet very slight. Kossel has shown that in fishes the nuclei 

 from which the sperm chromosomes are produced consist of combinations of 



