424 ANIMAL NATURE OF DIATOME^E. 



A. hyalina, by the same author. In respect to the 

 median lateral perforations, besides the already expressed 

 doubt whether they exist on both the primary surfaces 

 or only on one, it is also to be observed that they are 

 wanting in six, (A. veneta, A. ajjonina, A. coffeaeformis 



B. Fischeri, A. acutiuscula, A. borcalis,} out of the 

 eighteen species assigned by Kutzing to this genus. 



37. DIADESMIS. Individua navicularia in fa^cias 

 elongatas (biconvexas) arcta conjuncta; apertures media 

 singidares et terminates bince distinctce. 



In 1836, Kutzing published (Dec. xvi, n. 153) the new 

 genus Brachysira : "frons minutissima constituta efrus- 

 tulis paralleliter et irregulariter coadunatis." Now, in 

 his Monograph of Diatomese, he makes no mention either 

 of the genus or the species (B. aponina] which was 

 nothing more than N. appendiculata. Nay more, there 

 is enumerated among the Naviculeee the Braokgrira 

 serians of Brebisson, and Bailey's fine observation on 

 N. major (N. viridis, Ehr.) is suppressed, " that it is not 

 rare to meet with four, sometimes even eight, united 

 laterally." The genus Diadesmis is established, however, 

 in which the Naviculse are arranged in rows exactly as in 

 the species just described, only perhaps with more con- 

 stancy and regularity. Yet the foundation of this genus 

 is justified by analogy with other families, and by that 

 similarity of genus in the parallel series which perhaps 

 is supremely attractive in systematic classification. But 

 independently of the value of the genus, which I do 

 not controvert, the organic condition of this concate- 

 nation in the Diadesmce and Splienosirce seems to fur- 

 nish important considerations. If the central aperture 

 of the secondary surfaces were really stomatic, serving 

 to the ingestion of aliment, we might suppose that, in 

 respect to the individuals contained in the midst of 

 these fasciae., that, unlike the terminal ones, they took their 

 nutriment mediately. Although such a condition occurs 

 in other classes of animals, yet in our case it is purely 



