216 THE AMERICAN MONTHLY [September, 



shall do the same with a seemingly more difficult but really more 

 easy group or genus of Diatomacece^ the Schizonema. The 

 genus Schizo7ieina was founded by C. A. Agardh in 1S24 (Bot. 

 Zeit), and forms naviculoid frustules commonly existing in the 

 ocean or salt water in fronds or tubes. But they can, for the 

 same reason which I have shown in Homceocladia^ be classified 

 as Navicula. Then we come to the species. As W. Smith 

 says, " the fronds of this extensive genus were among the earliest 

 Diatomaceous organisms recognized by naturalists, and have been 

 the perplexity of all subsequent observers." He points out that 

 " their external form, size, and color vary with age, season, and 

 locality, and in consequence any characters based alone upon these 

 particulars are uncertain and deceptional." The genus must be 

 grouped together under Sckizotiema^ C. A. A., 1S24. By R. K. 

 Greville, 1826, under Schizonema and Monenia ; by C. A. 

 Agardh, 1S30, under Schizonema and Microtnega\ by C. G. 

 Eherenberg, 1S3S (Infr. ), mwA^x Nononema ^?iwAviO-w di% Navicula. 

 With the exception of Schizonema cruciger., W. S., 1S56, 

 which is now classed under Pleiirosigfna., W. S., by most ob- 

 servers, we can group the twenty-four Micromega^ F. T. K. , 

 1S44, under one head or species of Naviciila fcctida., J. E. S., 

 1790-1S14, which is Ulva ftvtida., J. E. S. That we will class the 

 Colleto7iefna^ A. de B., under this group along with Berkleya^ 

 R. K. G., and Dickieia^ J. R., is most certain, I think. For 

 they are formed in fresh water as Colletonema neglectum or C. 

 vulgare or C. subcohcerens. These are placed under Pintiu- 

 laria {Navicula^ radiosa and JVavicula crassiinervia. But this 

 part of the subject I do not wish to go into at the present time. 



I have the very large, middling, and small forms grow- 

 ing in one tube at the Passaic river, Newark, N. J., and Hudson 

 river at Fort Washington, N. Y , and growing with the Schi- 

 zonemas^ in the same tube, is the Homceocladias as I have designa- 

 ted. Now what can we say is a species in the Z>/fl;/o;«a(:e<zr.^ The 

 species cannot exist, and the genus breaks down, when we come 

 to apply the same mode of reasoning to that. In fact the whole 

 family of Daitomaceoe will break down, I think, when we come 

 to apply it to that also. 



Rjidiolaria : Their Life-History and Their Classification. 



By Rev. FRED'K B. CARTER, 



MONTCLAIR, N. J. 



\^Cotitinued from page 180.'] 



Finally if your form is 2ijlat disk and the surface of the disk on 

 the flat slides is covered by a porous sieve plate and the chambers 

 of the rings are imperfectly divided by the radial beams it is 

 exihitx Porodisczi^ ^^=FlustrcUa) ^ Po-ichlamydinm^ Stylodic- 



