Edwards.] 218 [February 9, 



collection of Colletonema vulgare, and for some time have been able 

 to keep it alive in a bottle so as to study its peculiarities. And here 

 let me say that many minute forms of both animal and vegetable life 

 which I have been unable to rear otherwise, I have found to flourish 

 in phials with small necks, or those with large ones, which have the 

 aperture partly stopped with a loose cover of some kind. It would 

 seem that the gases given off from the human body, and accumulat- 

 ing in dwelling rooms, in which I have kept specimens, are deleterious 

 to these small forms, and the partial closing of the vessel prevents, to a 

 great extent, their entrance. My specimens of Colletonema flourished 

 finely and greAV considerably. I have been thus enabled to watch 

 them, as I may say, building their tubes; this species, consisting of 

 naviculseform frustules enclosed and freely swimming about in tubes, 

 after the manner of Schlzonema. In fact there is nothing to separate 

 these genera, except that the first inhabits fresh water, whilst the 

 latter is an inhabitant of the sea, where it is to be found generally in 

 profusion, covering larger algas and rocks. The extension of the tube 

 takes places after the following manner. As the frustules increase by 

 the process of subdivision common to all of the Diatomaceas, of course 

 the two frustules thus formed occupy double the space of one, and as 

 the cell division is continually going on, after a time the tube must 

 become choked with individuals. At this period in their existence 

 they appear to be extremely active, moving with increased rapidity 

 up and down the tube as freely as their crowded condition will permit. 

 Whether the end of the tube is never closed, or opens at certain sea- 

 sons, I have been unable to determine; at all events it is now found 

 to be open, and the frustules slip over each other until they reach 

 this opening, and one or two will project outside as if prospecting, 

 and will occasionally return within the general envelope. When a 

 frustule thus projects from the open end of the tube, it never, as far 

 as I have seen, rushes onward with the vigorous motion with which it 

 moves Avithin the envelope, but this is doubtless only so when the tube 

 is being lengthened. It can be easily understood that if the species 

 be disseminated by the distribution of perfect frustules, as seems to 

 be most likely, that they must then escape from the tube after the 

 manner I have recorded above as taking place in the allied genus, 

 Schizonema. When one or two frustules have projected from the open 

 end of the tube, they often immediately come to a rest just beyond 

 the tube, or do so after moving over each other slowly outside of, but 

 in a line with, the tube. While at rest there appears to form around 



