ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 



107 



(2) Further, I was able to establisli the fact that there is a very 

 noteworthy difference in the oscillation of the micrococci according as 

 the alga is at rest or in motion. As long as the alga remained quiet 

 all the violently vibrating micrococci were symmetrically arranged 

 (Fig. 1) so that their vibrations ceased at an equal distance all round 

 from the surface of the cell. But an entirely different appearance was 

 displayed by the diatoms in motion (Fig. 2).* Here the dancing was 

 irregularly distributed, the most violent being concentrated at the pos- 

 terior end t of the alga. At this part it was most energetic, and could 

 easily be seen, even with a low power. Altogether the phenomenon 

 produced the impression as of a violent stream of water behind the 

 moving diatoms, which put the micrococci into irregular motion, and 

 extended a considerable distance (more than the total length of the 

 alga itself). At the same time a very slight movement of the micro- 

 cocci was noticed at the anterior end ; when the pause ensued the 

 vibration again became uniformly distributed, and on the commence- 



FiG. 2. 



Fig. 1. 



Fig. 3. 



ment of the retrograde movement the distribution of the vibrating 

 force of the micrococci was reversed. The end where previously 

 they were present in small numbers, moving with feeble oscillation 

 (the former anterior end), showed energetic vibrations, it having be- 

 come the posterior end ; and, conversely, at what was previously 

 the posterior end, where the motions were so energetic, they lost their 

 intensity, and only extended over an inconsiderable space. An in- 

 variable connection was always observed between the force of the 

 vibration of the micrococci and the direction of the movement of the 

 alga. The most violent vibration was always seen at the posterior 

 end of the diatom and the feeblest at the anterior end. 



This connection points plainly to the fact that the maximum 

 osmose is localized at the posterior end, where the discharge of water 



* The closeness of the dotting denotes the violence of the vibration of the 

 micrococci. 



t Relatively to the direction of movement. 



