CORRESPONDENCE. 279 



that Frustulia Saxonica and Navicula crassinervis are not the same 

 diatom, as follows.* " Dr. Rabenhorst discovered a certain diatom in 

 Saxon Switzerland and named it Frustulia Saxonica. De Brebisson 

 also, as I understand, discovered a certain diatom and named it 

 Navicula crassinervis, and did so under the impression that what he 

 so named was something totally different from what Dr. Rabenhorst 

 had called Frustulia Saxonica. Dr. Rabenhorst, again, in the letter I 

 read to you, says expressly, that he who identifies these two diatoms, 

 must be ignorant of one or other of them 



" Now, if there be any two greater Continental authorities than 

 Dr. Rabenhorst and the late De Brebisson, I should like to know 

 who they are." 



So far good. I accept the position. Let us see what these two 

 gi'eat Continental authorities really do say — not by letter, now when 

 they have forgotten what they have really said before (which indeed 

 is not remarkable for Dr. Rabenhorst, who is a most industrious com- 

 piler), but what they puhlislied, ivhen the subject teas under fresh inves- 

 tigation. First, Dr. Rabenhorst. In his latest publication on the 

 Diatomacefe, as a whole, 'Flora Europfea Algarum, Sectio I., Algas 

 Diatomaceas Complectans,' p. 227, he says, " Frustulia Saxonica, var. 

 c, forma aquatica (Navicula crassinervia Breb. 1852 ! in Sm. Diat. 

 p. 47, tat. xxxi. f. 271)," Observe, this has the botanical mark of iden- 

 tification ! and, curiously enough, he says, " striis ohsoletis, longitudina- 

 libus distinctioribus." How about the ignorance of the Doctor himself ? 

 But now, second ; the other " great Continental authority," and justly 

 so called. In a paper published in ' Ann ales de la Societe Phytolo- 

 gique et Micrographique de Belgique,' 1868, upon Vanheurckia, a new 

 genus of the DiatomacesB, Brebisson says, " V. crassinervia Breb. — 

 Nav. crassinervia Breb. MSS. W. Smith, Brit. Diat. i. p. 47, pi. xxxi. 

 f. 271 — Frustulia torfacea Braun, et Nav. Saxonica (Frustulia) Raben. 

 Diat. 50, t. 7." How about De Brebisson's ignorance ? 



Here, then, each of Mr. Hickie's authorities states that N. crassi- 

 nervis and Frustulia Saxonica are the same ; moreover, in Rabenhorst's 

 Algen, as stated by Grunow, Navicula crassinervis Breb. occurs in his 

 No. 48, as Frustulia Saxonica, and Grunow himself, quite as good an 

 authority, to say the very least, as Dr. Rabenhorst, states explicitly, in 

 " Ueber neue oder ungeniigend gekannte Algen," ' Verhandl. der K. k. 

 Zool. Bot. Ges.' x. B. 1860, p. 573, "Frustulia Saxonica Rabenhorst, 

 ist Navicula crassinervis Breb.," &c. Mr. Ralfs, who does not seem 

 to have examined any authentic specimens of N. crassinervis, but 

 gives Rabenhorst's description, remarks, in Pritchd. Infs. j). 924, 

 " F. Saxonica (Rab.) slenderer than F. torfacea," but the latter, he says, 

 " from an authentic specimen appears to be identical with Navicula 

 rhomhoides." I have already noted that De Brebisson considers F. 

 torfacea and F. Saxonica the same. Again, W. Smith, in the British 

 Diatomaceae, vol. ii. p. 69, suggests that Nav. crassinervia (this was 

 the original name, it should be "crassinervis") is the free state of 

 Colletonema vulgare, and in this he was undoubtedly right; and Donkin, 



* See ' M. M. J.,' March 1876, p. 127. 



