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MANN DIATOMS OF THE ALBATROSS VOYAGES. 369 



Mastogloia, but we can not for that reason divide X. cuspidala into two genera. In fact 

 in bonie species of Mastogloia we find a close appruxinialion to the craticular jilate by 

 the extension of the marginal ph^tes toward or to the center of the valve, as in M. 

 smilhii Tliwaiie^,^ a form called for that reason yaricala hiscalaris l>y Brebisson.^ - 



There is, however, some reason, despite the foregoing objections, for admitting the 

 genus, namely, Ihat true examples of Mastogloia always have, so far as I know, these 

 marginal internal loculi and are thereby rendered widely distinct in appearance from 

 any Xavicula, As for their mode of growth, i. e., the individuals being embedded in 

 gelatinous masses, this can not be taken into account here for the reasons mentioned 

 under Cocconema. Besides, asGrunow points out, ^" living wpecimenw of Mastogloia are 

 often found without this gelatinous matrix. It schmus best, on the whole, to re(*ognize 

 the genus sultject to the foregoing remarks. 



The admission of Ehrenberg's genus rhnirosiphonia as a synonym is also open to 

 question. Most authors overlook it entirely. Thus I can find no reference to it in 

 elevens extensive work on thenaviculoid diatoms. <^ De Tuni^ recognizes it as a distinct 

 genus with seven species, Ralfs, /though giving it a place in hi^ classification, says: 



"Tlie characters of this genus are unknown t(>us(they were not given by Ehrenberg till 

 ten years later — 1870); but from Ehrenberg 's figure of P. ajjinis we think it is probably 

 identical with Mastogloia." Even the diagnosis does not quite settle this doubt. 

 There is no exact mention of marginal loculi, but of '^siphons" (Avhence the name), on 

 either side as lateral lines. These, which Ehreid)crg states are ''saepe acre repleto/' 

 are so figured in all the above citations, and in every case they are drawn as within the 

 marginal space occupied by the loculi of Mastogloia; that is, nearer the center of ibe 

 valve; and invariably as unbroken tubes, not as rows of ( hambered loculi, a fact em]>ba- 

 si/.ed in the diagnosis by the word ''sim])lice.'^ 15u1 no such diatoms have ever been 

 met with. The nearest thing known is Mastogloia, luhI it is reasonable to suppose with 



m 



Ralfs that Ehrenlx^rg was dealing with specimens of Mastogloia. Pleurosiphonia ap- 

 pears in literature three years prior to the making of Mastogloia; that, is in 1853* But 

 this is without figure or description, a nomen nudum. Ehrenberg's figure prec-otles 

 Thwaites's publication by two years, but the diagnosis does not occur till 1870, under 

 the title ^'Xova Genera.'* (See citation above.) The generally recognized rule of bot- 

 anists that the date of a name shall rest on its diagnosis rather than on an undescribed 

 figure should not be used too strictly with the Diatomaceae; for, as a nde, figures are 

 worth much more than any diagnosis, as the intricate sculpture of the diatoms, on which 

 their genus and species depend, is possil>U* 1o figure but well-nigh impossible to 

 describe. Besides, the reason for this rule in higher plants, seed catalogues, and 

 similar non-srienti(ic publicationSj plays no part with the diatoms. I woidd not, 

 therefore, as a rule, make the diagnosis the chief I'aclor in fixing the date of a genus or 

 species in the Diatomaceae. But in this case, where the figures are at best indefinite 

 an<l the diagnosis does not appear till Unw years later than Thwaites*s accurate figures 

 and description, I give preference to the latter. 



Mastogloia lemnisca Lend. -Fort* Mem. Soc. Emu!. St. Brieuc 35. pL S. f. 29, 1879. 

 Schmidt, Atlas pi 186, f. 14-I0. 189:5, De Toni, Syll. Alg. 2: ?i2\. 1891. Cleve, 

 Sv. Vet, Akad. ITandb 27-': 159. pi. 2.f. 26. 1S05. 

 ^ty specimen exhi])its the markings of the variety reijresented by Schmidt's figure 14 

 above. 



Found at station ijObJII, Hawaiian Islamls, 



"W. Smith, Synop. Brit. Dint. 2: pi. S4.f, .IUI>- 185*) 



^In lit. January, 1853. 



cVerh, ZooL Bot. Ges. Wien 10: 575. bS6f). 



'^Sv. Vet. Akad. Handb 26-': 1894; 27=': 1895. 



<^DeToni, Syll. Alg. 2: 320. ISDL 



/Fritch. Hist. Infus. ed. 4. 915, 1S(;L 



