594 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



phylogenetic relationship of the species, but which, as in the egg yolk, does 

 not take a course quite parallel to the evolution for instance of the serum 

 proteins. In many cases it is not possible to distinguish between these accessory 

 and the primary organismal differentials, because of the impossibility of 

 carrying out the necessary experimental tests. Also, certain products of organs, 

 such as enzymes and hormones, so far as the latter are proteins, may possess 

 organismal differentials; but whether these differentials are of the first or 

 second type is unknown. 



There are present in various species other systems of differential substances 

 in which a much more limited parallelism exists between the chemical nature 

 of these substances and the phylogenetic relationship of the species. This is 

 the case, for instance, in some groups of higher organisms in which the 

 primary blood-group differentials bear specific relations to certain constituents 

 of the blood sera. Blood groups of the same kind are found in man and in 

 certain anthropoid apes, but these close similarities are lacking if man and 

 less nearly related species are compared. A still more limited parallelism is 

 shown between phylogenetic relationship and the distribution of the Forssman 

 heterophile differentials. Such partial parallelisms may be observed also be- 

 tween the evolution of organ differentials and of the interactions between 

 certain organs on the one hand, and phylogenetic relationship of the species 

 on the other. We have referred already to the observation of Sherwin, that 

 phenylacetic acid is detoxified in more primitive organisms, including monkeys, 

 by conjugation with glycine, leading to the formation of phenaceturic acid. 

 In human beings, it combines with glutamine and is eliminated in the urine 

 as phenylacetyl glutamine ; and according to Power a chimpanzee behaved like 

 man. Another example of a parallelism between the nature of metabolic 

 processes and phylogenetic relationship is the following : creatinine phosphoric 

 acid plays an important role in muscular contraction, but it is almost ex- 

 clusively found in vertebrate muscle ; in invertebrate muscle its place is taken 

 by arginine phosphoric acid. However, there are two important exceptions to 

 this rule. Creatinine phosphoric acid is also found in the muscles of some 

 echinoderms and of Balanoglossus. The latter is believed to represent a form 

 transitional between invertebrates and vertebrates. 



The distribution of urea and uric acid conforms only partly to phylogenetic 

 relationship; but there is a definite connection between the production of urea 

 or uric acid in certain classes or species of animals and the distribution of the 

 enzymes arginase, xanthine oxidase, urease, allantoinase and allantoicase. 

 Such a partial relationship applies also as far as the distribution of hemoglobin 

 is concerned. It occurs in the erythrocytes of all the vertebrates and in the 

 plasma of annelids and molluscs. In the corpuscles of annelids there occurs 

 the pigment hemerythrin, and in the plasma of gastropods and cephalopod 

 molluscs, as well as in the plasma of crustaceans and other arthropods, there 

 occurs hemocyanin. From such systems all kinds of transitions may be found 

 to an entirely random distribution of substances, without regard to phylo- 

 genetic relationship, as for instance, that found in the case of the heterophile 



