44 The Significance of Chemical Molecules 



j. Elsberg's Plastidules 



The most thorough attempts to explain the phenomena 

 of heredity by the qualities of the molecules of living 

 matter were made by Louis Elsberg and Ernst Haeckel. 

 Elsberg, who called the cells plastids, chose for the com- 

 ponent particles the name of plastid-molecule or, abbre- 

 viated, plastidule. 9 Haeckel considered this expression 

 a brief and suitable designation for the polysyllable pro- 

 toplasm-molecule, 10 and secured general consideration for 

 the term in his "Perigenesis of the Plastidule." 11 



According to Elsberg, living matter consists entirely 

 of plastidules which multiply in such a manner, through 

 nutrition, assimilation, and growth, that new molecules 

 with the same characters as those present, are constantly 

 developed. At each cell-division these are transmitted to 

 the daughter-cells. The resemblance of children to 

 their parents, grand-parents, and ancestors is explained 

 in a simple manner by saying that they are essentially 

 built up of the same kind of plastidules, which they have 

 inherited from their ancestors. All individuals of one 

 species consist, on the whole, and apart from incidental 

 varieties, of the same plastidules; every species, how- 

 ever, contains the plastidules of its whole ancestry, and 

 consists therefore, of as many different plastidules as 

 there were different species in this ancestry. The dif- 

 ferences between individual species are conferred by their 



9 Elsberg, Louis. Regeneration, or The Preservation of Organic 

 Molecules : a Contribution to the Doctrine of Evolution. Proc. 

 Amer. Assoc. Adv. Sci. 23: 1874; and Elsberg, Louis. On the Plasti- 

 dule Hypothesis. Ibid. Buffalo Meeting, August, 1876. 25: 178. 1877. 



10 Haeckel, E. Jenaische Zeits. Med. Naturw. 7: 536. 1873. 



"Haeckel, E. Die Peregenesis der Plastidule. p. 35. Berlin, 1876. 



