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same genus, and, if I am not mistaken, in the allied one, 

 Homoeocladia. 



After a time it would seem that the broken end of the 

 tube becomes closed again ; perhaps by the deposition of new 

 matter, or it may possibly be by the action of the surround- 

 ing 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 

 commonly 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 investing tube, it has not resulted from any rupture 

 caused by my manipulation, 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 believe that such 

 is the habit of all so-called epiphytaceous forms, otherwise 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 Schizonema apparently 

 perseveringly attempt to regain a lodgment within the tube 

 from which it had some time before escaped, by means of 

 repeated dives towards the hitherto open end, which has 

 since become closed. I have observed such struggles con- 

 tinue for a minute or more, but never with the success appa- 

 rently 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 apparently different genera of Diatoms existing 

 within the same investing tube, and now I wish to place 

 that fact upon record, and state one or two more instances 

 of the same mode of growth. During the month of March, 

 1868, I found in the harbour of New York specimens of 

 Schizonema Grevillei in active motion within their investing 

 tubes, but accompanied by a much smaller form possessing 

 a totally different outline from S. Grevillei, being blunter at 

 the ends, and with parallel sides on S. V. During the same 

 month, and also in April, I found this mode of occurrence 

 very common, and also Schizonema Grevillei and a Homceo- 



