PROF. STRASBURGER S OBSERVATIONS ON PROTOPLASM. 131 



regarded as a substance of great complexity of structure, and 

 this view becomes a conviction if the protoplasm of an ovum 

 be considered as the depository of the specific peculiarities 

 of the future organism. Let us take, as an illustration, the 

 Myxomycetes. The plasmodia of the various species of 

 these organisms differ but slightly from one another, when 

 their differences are compared with those existing between 

 the forms of fructification which these plasmodia bear. And 

 yet it cannot be doubted that certain differences, not to be 

 directly detected, but not the less real and active, exist 

 between the plasmodia, and are the agents in the produc- 

 tion of such variety in the fructification. We may regard 

 the molecules, the structural units of which protoplasm is 

 composed, as the bearers of these specific peculiarities, and 

 they have recently been recognised as centres of activity by 

 Elsberg^ and Haeckel,^ the name of " plastidules " being 

 given to them. That this is really the case is shown by 

 such facts as the following, for instance, that among the 

 Myxomycetes a single plasmodiuni may bear an unlimited 

 number of fruits, that a portion of a plasmodium is capable 

 of forming a fructification, that a single cell of some higher 

 organisms, such as a leaf-cell of Begonia ,is capable of re- 

 producing the plant, and especially in the reproductive 

 activity of spores and ova. All these facts lead to the con- 

 clusion that each of the structures in question contains 

 within itself the special peculiarities of the whole organism 

 of which it is a part. Farther than this we cannot go. We 

 do not know, and we cannot even imagine what mechanism 

 it is by means of which the process of development is worked 

 out, and heredity established. We know only the fact that 

 the course of development is under the influence of heredity. 

 We go on to assume that external conditions lead to the de- 

 velopment of new faculties in an organism,which process we in- 

 clude under the expression " adaptation to the environment," 

 but we do not know what is the molecular process by means of 

 w hich the organism thus responds to an influence acting from 

 without. This we know, however, that the changes, thus 

 produced, if they affect the whole protoplasm of the organism, 

 or at least the protoplasm of the sexual or asexual reproduc- 

 tive cell, are inherited by the succeeding individual. 



We cannot assume that all the parts of the organism have 

 their germs in the ovum, for such an assumption would com- 

 pel us to accept the view that, in the case of those organisms 



^ ' Proc. of the American Assoc.,' Hartford, 1874. 

 ^ 'Perigenesis der Plastidule,' 1876; see also 'Nature,' No. 350. July, 

 1876. 



