Protoplasm and Protein 41 



dividual bearers of heredity in the same cell, with the 

 exception of insignificant differences, are alike. Finally, 

 there is the directly opposite opinion of those investi- 

 gators who assume a special kind of material bearer for 

 every individual hereditary character; and according to 

 whom, therefore, protoplasm is built up of numberless 

 unlike hypothetical units. 



It is these three different principles that we will sub- 

 ject to a thorough comparative examination in this and 

 the two following chapters. Before doing so, however, 

 we must first critically consider the relation between pro- 

 tein substances and protoplasm. 



2. Protoplasm and Protein 



Lately the conceptions of protoplasm and protein have 

 been confused by many authors.^ This has led to the 

 hypothetical, and in no w^ay justified assumption of a 

 living protein.^ This usage has exercised its influence, 

 even on the theory of heredity, and for this reason it 

 should not remain unmentioned here. Without this con- 

 fusion, the view which regards the chemical molecule of 

 protoplasm as the bearer of the hereditary characters 

 would probably never have met with any favor. 



Protein is a chemical, protoplasm a morphological 

 concept. Chemistry is able to produce many pure pro- 

 teins, while the nature of protoplasm is conditioned by 

 its very heterogenous composition. Many protein bodies 

 can pass into solution, but nobody will ever think it pos- 

 sible to obtain a solution of protoplasm in a test-tube. 



^Haeckel refers to protoplasm as a protein body : Generelle 

 Morphologic. 1: 278. 



^A term proposed by Pfluger. Arch. Ges. Physiol. 10: 251. 1875. 

 Tr. 



