1870.] 213 (Edwards. 



and here and there will be seen individuals which at once alter the 

 direction of their course and move in exactly the opposite direction, 

 or backwards, as we may say. The individual frustules as they es- 

 cape from the ruptured end of the investing tube and enter the sur- 

 rounding water, do so with the peculiar trembling and apparently un- 

 certain movement so characteristic of many of these organisms. 



It will be well to note that these observations have been mainly 

 made on Schizo/ierna Grevillei, a species occurring very commonly in 

 New York harbor, although I have noticed the same thing to happen 

 with other species of the same genus, and, if I am not mistaken, in 

 the allied one, Homceocladia. 



After a time it would seem that the broken end of the tube be- 

 comes closed again; perhaps by the deposition of new matter, or it' 

 may possibly be by the action of the surrounding water upon the 

 fluid within the tube, if it be of a different composition (which would 

 seem to be extremely doubtful, however), as the frustules no longer 

 attempt to escape and resume their quiescent state from which they 

 have been startled by the accident of the rupture, or they move over 

 each other up and down with the same irregularity which is com- 

 monly the habit of these forms. 



I am strongly of opinion that certainly in some of the cases in 

 which I have seen this escape of frustules take place from the invest- 

 ing tube, it has not resulted from any rupture caused by my manip- 

 ulation, but would seem to be a normal occurrence. In fact, at such 

 times the diatom is taking upon itself the active or free condition by 

 means of which the species is to be distributed. And we must be- 

 lieve that such is the habit of all so-called epiphytaceous forms, other- 

 wise it is not easy to comprehend how the species become so wide 

 spread as many of them are, for we have not at present any authentic 

 notice of the formation of free swimming spores in this family. It is 

 hard when making such observations as those I have here recorded, to 

 believe that these organisms are not endowed with sentient capacities, 

 especially when one sees, as I have, a free frustule of such a Schizo- 

 nema apparently perseveringly attempt to regain a lodgement within 

 the tube from which it bad some time before escaped, by means of 

 repeated dives towards the hitherto open end, which has since be- 

 come closed. I have observed such struggles continue for a minute 

 or more, but never with the success apparently desired. 



Many months since I mentioned at one of the meetings of the 

 Lyceum of Natural History in New York, that I had seen two ap- 



