Edwards.] 214 [February 9, 



patently different genera of Diatoms existing within the same invest- 

 ing 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, 18G8, I found in the harbor of New York specimens of 

 Sclilzonema Grevillei in active motion within their investing tubes, but 

 accompanied by a much smaller form possessing a totally different out- 

 line 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 Homceocladia in the same tube, and Schizonema cruciger and 

 the small form mentioned above, both in the same tube, and & 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, 18G9, I found growing in the 

 salt water of the " Mill pond" at Salem, Mass., Schizonema cruciger 

 and Nitzschia closterium, W. S. (Ceratoneis closterium, C. G. E., and 

 Niizschiella closterium, L. R.), both in the same tube. And here it 

 will be necessary to say something in regard to the form I have called 

 Nitzschia closterium, as I shall thereby, I hope, be enabled to clear 

 away a little fog of synonyms. Neither Smith, Kutzing nor Raben- 

 horst describes or figures any species living within a tube like Schizo- 

 nema, the frustules of which have an outline and markings similar to 

 Nitzschia closterium, so that it is not likely that they ever saw any- 

 thing but the free form or condition of this species. However, 

 Ehrenberg figures and describes, under the designation of Schizonema t 

 Agardhii (Die Infusionsthierchen, 1838, p. 343, T. XX, fig. xvi), a 

 form agreeing with this, but the structure of the frustule is that of 

 Niizschiella 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 

 Homozocladia, it had better be placed in that genus, so that the syn- 

 onomy would stand thus. 



Homozocladia Agardhii, C- G. E. (sp.). Abhand. K. Akad. Ber- 

 lin, p. 311. 1833. 



Ceratoneis closterium, C. G. E. 1840. 



Nitzschia closterium, W. S. 1853. 



Niizschiella closterium, L. R. 1864. 



What are we to say to such facts as these I record, as well as that 

 of which I sent an account and illustrating specimens to the late Dr 

 Walker- Arnott, — and which has been noticed by Mr. R Kitton, who 



