410 ANIMAL NATURE OF DIATOME.E. 



in the minuter species renders uncertain the generic 

 arrangement of some among the fifteen species enu- 

 merated by Kiitzing. 



25. COCCONEMA. Individua ut in genere prace- 

 denti sed stipitata, stipite ex uno apice cymbellarmn 

 crescente. 



Without concerning ourselves with the generic value 

 of the character which is wanting in six of the eleven 

 species ascribed to Cocconemce, it is most interesting to 

 consider that whilst some Cymbettce adhere parasitically 

 to submerged bodies by their ventral surfaces, like Epi- 

 themice, the Cocconema, again, adhere with a stipes by 

 one of their extremities. Are we hence to infer that the 

 adhering side may be either one of the primary surfaces 

 or one of the secondary (Cocconoidese) or finally one of 

 the extremities ? Or must we regard adhesion as a 

 primary character in judging of the organographical 

 correspondence of the various surfaces and different 

 types, and make other characters subordinate to it, such 

 as the one derived from the division which sometimes 

 takes place in the direction of that surface, sometimes 

 transversely to it ? Again, admitting the first case, ought 

 we not, at least, to ascribe to this character a value 

 superior to that of the presence or absence (at least when 

 they are doubtful,) of the central and terminal apertures ? 

 Or, finally, that adhesion of the only species of Cymbella 

 which is said to be parasitic (C.pediculus), is it not merely 

 ventral in appearance, as seems sometimes to be the case 

 in certain Achnanthides ? 



26. STNCYCLIA. Individua cymbellij 

 in fascias circulariter in curvas connata, in substaniia 

 gelinea molli amorpha nidulantibus. 



The genus Syncydia (S. salpa, S. quarternarid) repre- 

 sents; among the Cymbelleae, the genus Eumeridion in 

 the order Astomaticae, the Epitliemia costata in the 

 family of Eunotiese. Whenever the lateral surfaces are 



