392 PROF. TH. W. ENGELMANN. 



ments after even some minutes of water-rigor. "When treated 

 for any long period with distilled water the protoplasm dies. 

 The phenomena attending this are not always the same. The 

 protoplasm may form vacuoles and deliquesce, or it coagulates 

 at once, in which case the form corresponding to the non-con- 

 tracted condition may remain preserved for a considerable time 

 longer. 



The withdrawing of water by indiflferent or diluted solutions 

 leads eventually to a temporary or lasting rigor (dry-rigor). 

 In vegetable cells, moreover, as discovered by Al. Braun^ in 

 Chara, the protoplasm generally withdraws itself from the cell- 

 wall as a continuous sac, the movements continuing for a 

 considerable time. Naked protoplasm (Amoebae, Myxomy- 

 cetes) which has been shrunk up by the action of 1 — 2 per 

 cent, salt solution often becomes covered with a large number 

 of fine, pointed, hyaline, cilia-like processes. After dilution 

 with water the protoplasm returns to its original condition.^ 

 Protoplasm which has been completely dried in the air at 

 ordinary temperatures and entered in consequence into rigor, 

 can under certain circumstances after mixture with water 

 become active again, and this even after several years. This is 

 certainly the case for instance with encysted Amoebse and 

 Infusoria. It may, however, be also observed in naked plas- 

 modia and in many other even quite highly organised bodies. 



It is important to note that when the concentration is excep- 

 tionally slowly increased, protoplasm can in many cases (all ?) 

 accommodate itself to the solutions, while if the action is more 



1 Al. Braun, 'Moaatsber. d. Berliner Acad.,' 1852, p. 225; further, W. 

 Hofmeister, loc. cit., p. 52. 



2 Kiihne, ' Untersuchungen, &c.,' pp. 48, 82 ; cf, De Bary, ' Die Myceto- 

 zoen,' 2 Aufl., p. 46, pi. ii, fig. 16 ; iii, figs. 11 and 12 ; Hofmeister, ' Die 

 Lehre von der Pflanzenzelle,' p. 24, fig. 28 ; V. Czerny, "Einige Beob. iiber 

 Anioeben.," 'Arch, f, mikr. Anat.,' v, p. 159, 1869; Strasburger, " Studien 

 iiber das Protoplasma," 'Jen. Zeitschr. f. Naturwissensch.,' x, p. 407, Jena, 

 1S76. The cilia-like processes are produced, according to most of these 

 observers, without any noteworthy change in the concentration of the sur- 

 rounding medium, in connection with a shrinking in of a process; this I can 

 also corroborate. 



