SECT. 15.] CONTRACTILE PHENOMENA. 2J 



cell-contents, or to the membrane, or to both. 2. Contractile 

 Fibre-Cells, in which the original cell, with the membrane and 

 contents, appears to have become converted into a soft, contractile 

 fibre; a merely elastic envelope has not yet, at least, been demon- 

 strated with certainty. 3. Cells composing the Hearts of certain 

 Embryos (Alytes, Sepia, Limax, Gallus), which, before they have 

 become converted into muscular fibres, accomplish contractile 

 movements. The energetic phenomena of contraction, which v. 

 Siebold has observed (compare my figure in Wiegm. Arch. xiii. 

 pt. i.) in the cells composing the young planarian embryos, are 

 generally reckoned under this head. Similar movements seem, 

 according to the more recent observations of many authors, to 

 occur in other cells; as, for instance, in the colourless blood- 

 corpuscles (Wharton Jones, Robin, Ecker, LieberTcuhn, Kolliker); 

 in the segments of the fecundated yelk of the frog {Ecker) ; in the 

 cells of Spongilla (Lieberkichn) ; in the pigment-cells of Batrachia 

 and of Chamceleo [Briicke, Virchow, Wittich, Busch, J. Lister); in 

 the corpuscles of the connective tissue of lower animals [Huxley ', 

 Busk, Kolliker) ; in the yelk of the eggs of fishes [Ransom, Rex- 

 chert), etc., etc. In some of these cells, the formation of real pro- 

 cesses, or prolongations of the membrane and contents, can easily 

 be shown ; but in other instances, as in the yelk of eggs of fishes, 

 and, according to J. Lister's observations, even in the pigment- 

 cells of frogs, the phenomenon consists only in a movement of the 

 granules of the cell-contents, without any changes in form of the 

 cells themselves. 



Among the phenomena of contraction which appear in cells, I 

 reckon, also, those of animal muscular fibres, which, as Remak 

 and I have shown, are nothing else than enormously-developed 

 single cells, with many nuclei; which cells, in some cases also 

 (insects, hearts of mammalia), coalesce, so as to form a network. 

 In fully-formed, transversely-striped muscular fibres, it is certain 

 that it is not the envelope representing the cell -membrane, the 

 sarcolemma, but the cell-contents, the jibrillce, which are con- 

 tractile; and thus it becomes probable that all contractile fibres of 

 higher and lower animals are similarly conditioned. In the 

 chromatophora of Cephalopods, and of some Pteropods, the change 

 of form docs not depend upon the cells themselves, but upon mus- 

 cular fibres attached externally to them [Kolliker, Harless, II. 

 .Vic Her). 



In a still higher degree than the motory phenomena of animal- 

 cells, which within certain limits also occur in plants (cilia of 

 spores, contractile spaces in Volvox, Busk), the very pccidiar pro- 



