OUTLOOK. 671 



find that if the proteins enter metabolism in any other way than through 

 the intestines, i.e., in such a way that the substances have not lost their 

 identity by the activity of the intestine and changed so that they are 

 suited to the body-albumin, then the only effect to be observed is the for- 

 mation of these specific products. This result supports our views regarding 

 the great importance of the digestion processes and assimilation in the 

 intestine for the maintenance of the species. 



With the assumption of atomic groups of specific nature in the individual 

 cells, and thus in the egg and sperm, new aspects are given to the problem 

 of heredity. Although it has not yet been found possible to cause mor- 

 phological changes that have been artificially produced to be inherited, 

 still there remains the possibility of effecting hereditary variations by 

 influencing the chemical composition. We may mention the interesting 

 experiments of Engelmann and Gaidukow l who succeeded for the first 

 time in proving satisfactorily that a property which had been acquired 

 could be inherited. If cultures of Oscillaria sancta, a kind of alga, are kept 

 for months at a time in light of a definite color, then the single threads of the 

 alga gradually assume a complementary color, i.e., a shade which is favor- 

 able to the assimilation in such light. The change of color takes place only 

 with the living organism. Aqueous solutions of the dye do not show any 

 such change in shade under the same conditions. We have, therefore, a 

 case of a vital, physiological adjustment. Engelmann designates it as 

 chromatic adaptation. Now, strange to state, this acquired change of color 

 is retained when the Oscillaria are placed in ordinary light. In the case 

 of rapid propagation, the new color prevails, so that the assumption may 

 be made safely that there is a new formation of chromophyll in the younger 

 generations of cells. In reality we have here a case of the inheritance 

 of a. change in chemical composition, and in fact in the formation of a 

 pigment, the synthesis of which remains the same as formerly in the new 

 environment. 



It might have been thought that by feeding compounds of quite definite 

 composition it would be possible to effect a change in the chemical compo- 

 sition, and thereby in the cell-metabolism. Such experiments must be 

 without much prospect of success, because of the fact that, as we have 

 seen, the intestinal wall frustrates the entrance of such foreign substances. 

 The unicellular beings are likewise unsuitable for deciding such questions, 

 because they are also provided with the necessary means for maintaining 

 their constancy of chemical composition. At best, the only way we can 

 conceive of any such experiment being successful would be to continue for 

 a long time the introduction of such substances to the body-cells in some 

 other way than through the alimentary canal, for it would be expected that 



1 T. W. Engelmann: Arch. Anat. Physiol. 1902, Suppl. 333. Sitzsber. Berliner Akad. 

 Wissensch. 1902. Arch. Anat. Physiol. 1903, 214. 



