76 SOLUTIONS AND PROTOPLASM [Cn. Ill 



the whole form of the organism has been likened to a horse- 

 chestnut with its shell on. (!VUHNE, '64, pp. 48, 83; CZERNY, 

 '69, p. 159.) ZACHARIAS ('84, p. 254, and '88) has described a 

 similar phenomenon in the spermatozoon of Polyphemus pedicu- 

 lus. When put into a 3% NaCl solution the spermatozoa lost 

 their cylindrical form and protruded long pseudopodia. A 

 remarkable fact about the pseudopodia, moreover, was that in 

 locomotion they were used like flagella. Likewise, FABRE- 

 DOMERGUE ('88, p. 102) and MASSART ('89) have observed 

 that the protoplasm of encysted Ciliata swells or contracts 

 according as it is placed in a less or more dense medium ; the 

 cyst thus being perfectly permeable by water. MASSART has, 

 indeed, obtained a rough quantitative expression of this state- 

 ment, which is given in Tables X and XI, p. 87. HAMBUR- 



FIG. 9. Blood corpuscles of the frog. 1, 2, normal; 3, 4, 5, various degrees of 

 plasmolysis by solutions. o, nucleus and shrunken plasma; b, water-filled 

 spaces. (From HAMBURGER, '87.) 



GER ('87) has found that dense solutions produce the same 

 modifications upon blood-corpuscles (see Fig. 9). 



Again, GRUBER ('89) has found those individuals of the 

 heliozoon Actinophrys sol which live in fresh water different 

 from those which live in the sea, and he has produced that dif- 

 ference artificially. In the marine variety the plasm is dense, 

 granular, free from vacuoles ; while that of the fresh- water 

 kind is extraordinarily rich in vacuoles, and has even a foamy 

 appearance. If a marine form is gradually accustomed to fresh 

 water its protoplasm soon acquires a vacuolated structure which 

 renders it indistinguishable from the fresh-water one. GRUBER 

 also accustomed fresh-water Actinophrys to sea water, when it 

 acquired the structure of the normal marine form. Likewise 

 the marine Amceba crystalligera, which has a dense protoplasm, 

 becomes vacuolated after being accustomed to fresh water. 

 Also, SCHMANKEWITSCH ('79) has found that when the fresh- 



