8 The Microscope. 



they are occasionall}^ in motion. Tliis may or may not be 

 imparted to them by the numerous Bacteria refrin;jentes among 

 them. They are of variable size, from 2 to 5;/ in diameter (the 

 globular bodies), but oftener the}^ are ovals 4, 5, 6, 8, 9,a long 

 by 3, 4// wide; sometimes we find one much larger, containing 

 two or three nuclei, the species perhaps new ; if so, ma}^ it be 

 named Micrococcus giganteus. When contrasted with the spores 

 of the mould growing on one batch of these onions we observe 

 the mould spores averaging larger, 6 to 10,a long, by 5 to 8// 

 wide, ovals with a thicker cell wall and yellowish, granular, pro- 

 toplasmic contents and no nucleus, and growing on threads of 

 mycelium, while the Micrococcus is in the juices of the onion 

 and with no mould threads. By these characteristics we can 

 distinguish them when mixed together in a mount. I kept one 

 of my best slides three days in the same damp box with the 

 slide of B. refringente, when I found it literally swarming with 

 this form of bacterium ; the water about the specimen was so 

 filled with them that I scarcely saw any open spaces under five 

 hundred diameters. These new individuals had very light 

 shaded contents, and being younger were ver}^ much more active 

 than those in the previous mount. 



It has been hinted b}^ one correspondent of The Microscope 

 that osmosis is the cause of the movement in the cells. To test 

 this question, I mounted a film of onion in the expressed juice 

 of the same onion to eliminate the possibility of osmosis, the 

 mounting medium being the same as the cell sap, or at least its 

 native environment. This, like the water-mounted specimen, 

 was quiet at first, and for at least two hours while under observa- 

 tion. But after twelve hours I again had time to examine the 

 specimen, which I found activity restored, and the streams of 

 protoplasm flowing magnificently. It was one of the very best 

 I ever saw ; a sight hard to break awaj^ from even at the mid- 

 night hour. Here there could have been no osmosis, the medium 

 in the cell and on the outside beino- the same. This mountino^ 

 medium is the very best for this exhibition, but it dries out very 

 soon, and I found after twenty-four hours more that the proto- 

 plasm had began to contract inwardl}^ from the ends of the cells, 

 for from one-eighth to one-fourth of the length of the cells. The 

 streaming had ceased, but the little bacteria [M. germinatus) 

 were still in motion. At the end of the second day the separa- 



