THE GERM-PL.ASM 4I 



and he looks upon them as being intermediate between the 

 chemical units (molecules) and the morphological units (cells). 

 But he supposes their function in heredity to be different from 

 that which I ascribe to my biophors. Haeckel * understands by 

 the term 'plastidule." introduced by Elsberg.f the hvpothetical 

 ultimate particles of which • protoplasm ' is composed ; he re- 

 gards them as equivalent to the -molecules' of inorganic matter, 

 but supposes them to possess ' vital qualities ' as well. Of 

 course this definition is in itself insufficient proof, as de Vries 

 very correctly remarks, that Haeckel" s plastidules are not mole- 

 cules in the physical sense; these very ^ vital qualities' are 

 the point in which they differ from them. 1 could not adopt 

 Nageli's term either, because a -micella' differs essentially in 

 its construction and properties from a biopho B) It is defijied 

 as -a minute crystal, microscopicall y invi sible, consisting of a 

 larger or smaltenTumber of molecules, and is, when turgid, 

 surrounded by a layer of water.' J As regards the absolute size 

 of the micella, Nageli calculates that it may consist of one hun- 

 dred molecules, or on the other hand, of only a single molecule 

 of albumen. As in the case of Haeckel's plastidules, we have 

 here therefore to deal with a unit the vital character of which 

 does not depend on a peculiar grouping of several or even 

 many different kinds of molecules. Indeed Nageli draws atten- 

 tion in another part of his book (p. 63) to the unstable chemi- 

 cal composition of the proteids so far as can be made out 

 by analyses, and very correctly considers it extremelv proba- 

 ble -that there are various molecules of albumen which differ 

 from one another in containing unequal quantities of hvdroeen, 

 oxygen. &c.' This leads him to the further assumption • that 

 the micellae of the proteids consist of a mixture of two or 

 more different kinds of molecules of albumen. In each proteid 

 the different molecules of albumen would be mixed in special 

 proportions, and, further, each would contain special quantities 

 of phosphates, .salts of magnesia, lime, and so on." This con- 

 ception, however, hardly agrees with that of the * crystalline ' 



* Ernst Haeckel, ' Die Perigenesis der Plastidule,' Berlin, 1876. 



t Louis Elsberg, ' Regeneration ; or. The Preservation of Organic Mole- 

 cules ; a Contribution to the Doctrine of Evolution." — Proceed. Am. Assoc. 

 for the Advancement of Science, Hartford Meeting, Aug. 1874. 



X Carl Nageli, ' Mechanisch-physiologische Theorie der Abstammungs- 

 ehre,' Miinchen u. Leipzig, 1884, p. 35. 



