Naviculacea.'] infusorial animalcules. 497 



RiiAPHiDOGLCEA manipuldta. — Globose, fusiform; rays of fasi>',lcs 

 reticular, not interrupted ; naviculae linear-lanceolate, obtuse. Length 

 l-TOOth to l-290th. 



E.. interrupta. — Pisiform; fasicles slender, interrupted in a joint- 

 like manner, their divisions tapering ; naviculije linear, truncate, and 

 rather attenuate at each end. Length 1 -300th. 



R. micans = Xaiinema micans (Ehr.) — Subglobose; fasicles large, 

 in irregular obsolete rays, naviculae linear-lanceolate, subulate, long, 

 and rather acute. Length l-144th. 



Genus ScHizoNEMA. — Envelope double, inner one sOi(;eous, navicula- 

 shaped; the external gelatinous resembling that of Naunema, but 

 the tubes are connected together in a bundle-like manner, not branched, 

 though they appeal- so when spread out. This description is as given 

 by Ehi-enberg, but that great observer had, at the date of his work, 

 1838, given less attention to this genus and to the other compound 

 forms of Diatoma, of which it may be taken as the type, than to the 

 other genera of this section. On the other hand, Kiitzing appears 

 to have more fully studied them, and has added very much to their 

 numbers. Thus he has collected twenty-six species of Schizoneina, 

 when only one was given by Ehrenberg ; and it so happens that this 

 very one is transferred by Kiitzing to the allied genus Micro meg a. 

 Although, therefore, Kutzing's account of Schizonema, as also of 

 Micromega, is not perfect, and errors have been detected by naturalists, 

 yet it is the best presented to us at present, and we shall therefore 

 give it concisely. Besides the twenty-six species from Kiitzin'T, 

 we are able to add several from that excellent observer, Mr. Thwaites, 

 and one recently described by M. Montague. 



Kiitzing defines Schizonema as a compound frond, filiform, slender, 

 lax; composed of gelatinous branched tubes (ccelomaj, inclosiac 

 longitudinal rows of short navicular bodies. Spores (spermatia) 

 simple, external to the tube, on which they are sessile. 



This genus gives name to the sub-section of Naviculae, the Schizo- 

 nemece, which embraces FrmtuUa, Borkeleya, RhaphidogLea, Homeo- 

 cladia, Schizonema, Micromega, and Dickieia, genera all possessiu"- the 

 double lorica of Ehrenberg ; in other terms, composed of navicular- 

 shaped corpuscles, imbedded regularly or irregularly in a gelatinous 

 substance. These forms superficially, and to the naked eye, resemble 



