158 F. 0. BOWER. 



agents to them is, however, a matter of difficulty, as, under the 

 action of reagents which injure living protoplasm, they assume 

 a ropy appearance, and often break away, while they refuse to 

 take up neutral colouring matters. It has been ascertained 

 that they stain slightly brown with iodine solution, while they 

 give a characteristic reaction with gold chloride.' 



It has been stated above that the strings, which are at first 

 as a rule extremely thin, become more obvious a short time 

 after plasmolysis, there being usually a marked change in the 

 first quarter of an hour (fig. 11). This is due to an increase 

 in thickness of the strings, which might be produced by either 

 of two processes, or by both simultaneously — (1) by the supply 

 of fresh substance from the main protoplasmic body ; (2) by 

 the lateral coalescence of two or more originally separate 

 strings. 



Exact observation shows that the first process does take part 

 in the change. It has been noted above that nodal swellings 

 are sometimes to be found on the threads. By fixing the 

 pointer of an indicating eyepiece upon one of these swellings, 

 on a thread of a recently plasmolysed cell, and watching it for 

 a period of a quarter of an hour or more, it has been seen and 

 verified in a number of instances that the nodal swelling moves 

 slowly from the main mass of protoplasm. Since the motion 

 is, as far as my observations go, always from the main mass of 

 protoplasm, we have thus an indication of the supply of fresh 

 substance from it to the threads, which may account for the 

 increasing prominence of the latter. The lateral vibratory 

 motion, which is seen in the strings some time after plasmo- 

 lysis, but is not so marked or is absent immediately after the 

 contraction, has been alluded to above. From these move- 

 ments it is inferred that the strings, though apparently 

 tightly stretched at first, become gradually slacker as time 

 goes on, a conclusion which harmonises with the observations 



' The method adopted was as follows : after plasmoljsis with 3 per-cent 

 salt solution treat with a solution containing 3 per cent, salt and 1 per-cent. 

 gold chloride, then wash with water and expose to the light in very dilute 

 acetic acid. 



