ANIMAL NATURE OF DIATOME^E. 451 



the French. We are induced to form this opinion by 

 the observation of Harvey, " The frustules are larger 

 than in S. Smithii, longer and blunter, double, and 

 rather densely set." This is applicable to the specimen 

 from Berkeley, but not to this one of Chauvin, which 

 ought to be authentic. 



Very different, both in external appearance and in the 

 extreme tenuity of the threads (fill), is another Schizo- 

 nema, also from the Coast of Calvados, obligingly supplied 

 by Lenormand, with the name Schizonema helmintosum 

 var. Chauv., in which the Naviculse are '01 85 in length, 

 and O'OOb* in breadth, as well of the exactly linear 

 primary surfaces, as of the elliptical secondary. The 

 partial tubes embrace the navicular series closely, and 

 frequently after, when the Naviculae have escaped, 

 contract into fine threads or become deformed and 

 wasted. 



Schizonema laciniatum* Harv. 



I received specimens of this beautiful species from 

 Harvey himself, and found the Naviculae 0'027 long, 

 and 0*007 broad, in the primary surfaces, which are 

 almost exactly linear, and in the elliptico-rotundate 

 secondary 0-0065. This agrees with Harvey's observation 

 " Frustules very minute and exceedingly numerous." This 

 would seem to refer to a species different from that de- 

 scribedandfiguredby Kiitzing, with thename 8. scoparium, 

 in which he says the Naviculae are ^th of a line in length 

 = 0'054 millim., and to which he assigns as an uncertain 

 synonym this of Harvey, and the 8. Smithii of Mrs. 

 Wyatt, (Alff. Danm. No. 151), which, according to the 

 indication of Harvey, would rather seem to belong to the 

 one before mentioned as S. sirospermum. 



Schizonema mucosum, Klttz. 



From Kiitzing's figure we should be induced to suspect 

 the presence of partial tubes in this species also. As to 



