140 W. JOHANNSEN 



To my mind the main question in regard to these units is this: 

 Are the experimentally demonstrated units anything more than expres- 

 sions for local deviations from the original (»normal») constitutional 

 state in the chromosome? 



Is the whole of Mendelism perhaps nothing but an establishment 

 of very many chromosomical irregularities, disturbances or diseases of 

 enormously practical and theoretical importance but without deeper 

 value for an understanding of the »normal» constitution of natural bio- 

 types? The Problem of Species, Evolution, does not seem to be approa- 

 ched seriously through Mendelism nor through the related modern 

 experiences in mutations. Here again the word »normal» was used! 

 It is a dangerous and somewhat illegitimate expression in Experimental 

 Biology. Carnivorous animals, gnats, protozoa and bacteria etc. are 

 »normal» beings, hence in Nature it is »normal» that several individuals 

 are devoured, attacked by malaria or tuberculosis! Degeneration and 

 mutations may be as »normal» as other results of combinations, sepa- 

 rations, non-disjunctions etc. in the processes of gametogenesis and fer- 

 tilization. »Nature is beautiful, but not correct» as a Danish saying 

 goes. »Degeneration» or »Evolution» may be used respectively as 

 terms for a given genetic process — depending on whether our more or 

 less subjective valuation emphasizes a »bad» or »good» tendency! 



Chromosomes are doubtless vehicles for »Mendelian inheritance», 

 but Cytoplasm has its importance too. I cannot here enter into this 

 problem from which in the near future we shall certainly have impor- 

 tant news. Gametogenesis with chromosome-reductions, accompanied 

 by reformations and, as it were, partial rejuvenescence of cell-structu- 

 res, must in some way act as if especially organized for obliterating the 

 individual's personally »acquired characters», which as a rule totally 

 disappear in sexual reproduction — quite contrary to the popular tra- 

 ditional Hippocratic-Lamarckian views. Cytoplasm is perhaps more 

 prone to »memory»; Jollos's experiments with Infusoria for instance 

 seem to suggest such a case. 



Continuity in inheritance, the cardinal idea of Aristotle, is — as 

 applied to Mendelian heredity — represented by the continuity of chro- 

 mosomes in the forthcoming generations — but greatly complicated 

 by disjunctions and recombinations of chromosome-pairs. This here- 

 ditary continuity is, in so far dissolved into a kind of regular periodic 

 discontinuities: Mendelian heredity always operating with discreet ge- 

 notypical elements. Hence differences are here always discontinuous 



