INFLUENCE OF THE COLOUR AND INTENSITY OF THE LIGHT. 613 



in ordinary white daylight. When, on the contrary, the light passed through a 

 concentrated solution of potassium bichromate, which transmits green, yellow, and 

 red rays, the swarm-spores did not react at all, and the same was the case 

 when the light was allowed to act through a ruby glass, which transmits essentially 

 only dark-red and green light, or when he allowed the nearly pure }ellow light 

 of incandescent sodium vapour (of a sodium flame) to act. 



Finally, as regards the intensity of the light, it is to be remarked in the first 

 place that the swarm-spores in the dark move in all directions, in curved and often 

 sinuous paths, and only come to rest when they perish, or in any way become 

 fixed. . The particular intensity of the light which influences the direction of 

 their movements at all differs, according to Strasburger, in different species. 

 Chilo?)ionas ciirvata on cloudy days did not collect at all at any particular margin, 

 but remained distributed throughout the entire drop; when the sky brightened, 

 however, they travelled to the light side of the drop. The swarm-spores 

 of Bcemaiococcus, on the contrary, became aggregated at the illuminated 

 margin of the drop, when the light 

 was scarcely bright enough to read 

 printed matter by. 



Amoeboid movement is the name 

 given to the locomotion of small free- 

 living protoplasmic bodies, which, ac- 

 cording to their nature otherwise, might 

 also be fitly designated swarm-spores, 

 and in fact some of them proceed from 

 such as later stages of development, 

 as shown in Fig. 360. Here are to be 

 mentioned particularly, the so-called 

 Myxamoebae — i. e. the early develop- 

 mental stages of the Myxomycetes. 

 In contrast to the true swarm-spores, 

 the relatively rigid bodies of which, 



as it appears, are made to move forward passively, by means of the vibrations 

 of the cilia, the amoeboid movement consists in the protoplasmic body (which is 

 sharply defined, however) adhering to a solid substratum, altering its external form 

 and creeping along the substratum, the peripheral portions of protoplasm being 

 put forth at some parts of the margin, and withdrawn at others ; and so the mass 

 slowly moves from place to place. This form of movement will perhaps be best 

 illustrated by comparing figures 9-12 in Fig. 360. As to the mechanics of such 

 movements there is practically nothing known, although for twenty years repeated 

 attempts have been made to explain them ^ 



album (after Cienkowski). i, spore ; a, 

 3, the free contents; 4, s. the same as 

 swarm-spore with one flagellum ; 6, 7, the same after losing their 

 flagella; 9, :o, 11, fusion of amcebae; 12, a small Plasmodium. 



1 That an explanation of the amoeboid movement of protoplasm and its circulation in the cells 

 is not obtained by ascribing ' contractility ' to the substance was insisted on by Hofmeister (' Flora,' 

 1865, p. 8). I attempted at the same time in my 'Handb. der Exp.-phys.'' (1865, p. 454) to replace 

 the indefinite idea connected with the word contractility by more definite assumptions, which of course 

 did not reach beyond the region of mere hypothesis, though they have so' far not been replaced in 

 their turn by better. I therefore quote the most important ones. ' I imagine that living protoplasm 

 consists of molecules of definite form (not round), but not capable of imbibition ; these have a 



