vii ORIGIN OF STRIA TION 329 



the whole the former means the muscle-cells, the latter the 

 muscle -fibres. But from the comparative standpoint this 

 division is quite unjustifiable, for there are transversely 

 striated muscle -cells as well as striated muscle -fibres, and 

 there are also unstriated, smooth muscle-fibres (Ctenophora). 

 Moreover, every one who has carefully pursued comparative 

 studies of muscles will agree with me that the transverse 

 striation arises gradually, so that transitions occur between 

 striated and unstriated musculature. Thus the distinction 

 between muscle-cells and muscle-fibres can only be admitted 

 as in accordance with fact, if it is understood that the former 

 are uninucleate, the latter multinucleate, since there are 

 simple uninucleate muscle-cells which are so elongated that 

 they might equally well be called fibres in the ordinary sense 

 of the word. 



On the other hand, recently histologists speak more 

 than formerly of the "muscle-prisms" (muskelkdstchen) as 

 the fundamental element of the striated muscle-fibre. But 

 the fibril is rather to be considered as the fundamental 

 element, and comparative observation leads necessarily to 

 the conclusion that the subdivision of this fibril into single 

 successive rods, which seems to exist in the most highly 

 developed condition of striation (the fact is still not abso- 

 lutely decided), can only be something acquired at a late 

 stage of evolution, and that at earlier phylogenetic stages it 

 does not occur at all. 



Thus I have already in my work on the Medusa; 

 advanced the proposition, and endeavoured to prove it, that 

 the striation of muscle is produced through its own activity, 

 is therefore an acquired and inherited character. 



The evidence for this lies in the following : (1) Striated 



manent intermediate stages of form between uninucleate muscle-cells and connec- 

 tive-tissue-cells, and therefore no sharp distinction between the two." Zeitschr. 

 f. wiss. Zoologie, Bd. xxx. Supplement, 1878, p. 473. 



