ANIMAL NATURE OF DIATOME^. 427 



H. lieloides pumila, parasitica, adnata, fills tenuibus 

 e centra radiantibus, dichotomis sensim attenuatis; syne- 

 dris, continue fasciculatis, mediocribus, e facie linearibus, 

 e latere oblongo ellipticis, obtusis. 



Schizonema helioides, Zanard, in litt. Ad Uloam latis- 

 simam legit Dalmatiae Sandri. Frons. 3 mill, vice attingens 

 Rivularite adspedum omnino prcesefert. Fila ad basim 

 0'02 mill, vix crassa et, ut in Rivulariis, rotundata. 

 Lonc/itudo Synedrarum 0'039 mill, latitude 0'0043 mill. 



In this genus, too, we may notice the greatest variety 

 of dimensions. Thus, for example, Kiitzing gives the 

 length of the Synedra of H.pumila ~", which, referred as 

 he states to the Paris line, corresponds to - 079 millim. 

 But in the .figure with an amplification of 420 linear, it 

 only equals O016 met., and therefore corresponds to 

 0'03S3 millim. Now I find the length to vary in my 

 specimens from 0-0457 millim. to 0'078 millim., and 

 therefore not far from the extremes above described. 

 This same species also presents in its thick inferior 

 trunk, and in the fasciculato-fusiform disposition of its 

 Synedrae, rather more relation to the two preceding 

 genera. Kiitzing refers my Schizonema ruorum to this 

 genus Homceocladia ; and justly, for it certainly does 

 not belong to the Schizonemae. But I think he might 

 just as properly refer it to the Berkley &> on account 

 of the thickness of the walls of the mucous threads, and 

 the uniform confusion (affastelmento) of the Synedrae. 

 As to the dimensions of these last, Kiitzing says they 

 correspond to those of the Rapliidoglcea interrupta ; but 

 this accords little with Kiitzing's figure magnified 420 

 linear; this is 0'023 metr., and therefore corresponds to 

 0'054 millim. ; it accords much less with the measure- 

 ment indicated Q/"), which is = O'lOS millim., though 

 the greatest length of these Synedrse in my H. lubrica 

 is = 0'04 millim. Of the seven species yet known in 

 this genus, two only (anglica, Martiana,} present mar- 

 ginal striae on the lateral surfaces ; this makes them far 

 more similar to the Synedra. 



