ee ee Notes on Diatomacee. 35 
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 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 
apparently different genera of diatoms existing within the same in- 
vesting 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 Grevillet in active motion within their in- 
vesting tubes, but accompanied by a much smaller form possessing 
a totally different outline from S. Grevillei, being blunter at the 
ends, and with parallel sideson 8. V. During the same month, and 
also in April, I found this mode of occurrence very common, and also 
Schizonema Grevillet and a Homeocladia in the same tube, and 
Schizonema cruciger and the small form mentioned above, both in the 
same tube, and S. cruciger and Grevillei in the same tube. In all 
these cases the frustules were in lively motion, passing over each other 
from one end to the other of the tube. In May of the present year 
(1869), I found growing in the salt water of the “ Mill pond” at 
Salem, Mass., Schizonema eruciger and Nitzschia closterium, W.S. 
(Ceratoners closterium, C. G. E., and Nitzschiella closterium, L. R.), 
both in the same tube. And here it will be necessary to say some- 
thing in regard to the form I have called Nitzschia clostertwm, as I 
shall thereby, I hope, be enabled to clear away a little fog of synonyms. 
Neither Smith, Kiitzing, nor Rabenhorst describes or figures any 
species living within a tube like Schizonema, the frustules of which 
have an outline and markings similar to Nitzschia closterium, so 
that it is not likely that they ever saw anything but the free form 
or condition of this species. However, Ehrenberg figures and 
describes, under the designation of Schizonema? Agardhii (Die 
Infusionstheirchen, 1838, p. 343, T. xx., fig. xvi.),a form agreeing 
with this, but the structure of the frustule is that of Netzschiella of 
Rabenhorst, so that the specific name of this species should be 
Agardhii, whatever its genus be decided to be hereafter. For the 
present, as it is nearest allied to the forms grouped under Homeo- 
cladia, it had better be placed in that genus, so that the synonomy 
would stand thus :— 
Homexocladia Agardhiit, C.G.E. (sp.). Abhand. K. Akad, 
Berlin. P. 311. 1833. 
Ceratoneis closterium, C.G. E. 1840. 
Nitzschia closteriwum, W.S. 1853. 
Nitzchiella closterium, L.R. 1864. 
What are we to say to such facts as these I record, as well as 
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