76 FRANCIS DARWIN. 



Dipsacus, dilute solutions of certain reagents produce con- 

 traction, A preparation was irrigated with 2 per cent, solution 

 of carbonate of ainmoiiia, which produced contraction. The 

 same result followed irrigation with 3 per cent, acetic acid. 

 Aqueous solution of sulphate of quinine (about -|'^ per cent.) 

 produced contraction. Aqueous solution of camphor (about 

 -j'o^ percent.) produced contraction. Methylated spirit produced 

 contraction. In their sensitiveness to very dilute solutions of qui- 

 nine and camphor we have another striking point of resemblance 

 between the lilaments of Agaricus and those of Dipsacus. 

 Ilotl'mann found that water at 30° C. causes violent contraction. 

 Warm water at various temperatures under 57° C. produces con- 

 traction of the Dipsacus filaments. Again, as in Dipsacus, 

 strong pressure makes the filaments run together into lumps. 

 (Hoffmannj p. 862.) 



The question — What do the filaments consist of, and what is 

 the nature of their movements ? presents precisely the difficul- 

 ties which I have attempted to discuss in the case of Dipsacus.^ 

 The opposing theories being, as in that case — (1) that the 

 filament contains irritable living matter ; in other words, that it 

 is protoplasmic ; and (2) that the movements are mechanical, 

 and due to the loss and gain of water. In the later of the 

 above-cited papers Hoffmann concludes that it is a pure "im- 

 bibition phenomenon, although of the most remarkable kind.'' 

 This does not seem to have been his firs;t impression, as he says 

 lit. Zng., 1853, p. 8()3j, " It seems to me that we have here un- 

 doubtedly the contractile substance, or a substance closely re- 

 lated to it, whose very general occurrence in the animal kingdom 

 Dujardiu demonstrated, and which was called by him " sarcode." 



On the other hand, De Bary is strongly of the opinion that 

 the filaments are not protoplasmic, and that the movements are 

 due to the imbibition or discharge of water. 



In his opinion" they are similar to the movements of myelin, 

 as described by Beneke.* He states thiit the substance of which 

 the filaments are conij)osed is nearly all soluble in alcohol and 

 ether, but that a small remnant is left which stains yellow in 

 iodine. If the slimy coating of an entire stalk is extracted with 

 absolute alcohol and evaporated the residue consists of irregular 

 granules and spheres of a substance melting easily, burning with 

 a bright llame and feeling sticky, but giving no oily stains to 

 paper. It may therefore be called resinous. lie beLeves that 



' Loc. cit., p. 264. 



^ ' Die Mjcctozocn,' p. 113. 



' Myelin is prepared by eva|)oratiiig an alcoliolic extract of the yolk of 

 hens' eggs. Wiien treated with water remarkable changes occur, liiamenta 

 growing out and exhibiting a species of movement. The (ilamcats, as figured 



