ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 247 



mediate forms. The inner side of tlie valve is here covered with 

 small dots or depressions, which form a circle of larger dots at the 

 margin of the meshes, gradually diminishing in size and becoming 

 scarcely visible towards the interior, but always covering the whole 

 of the base of the meshes. On closer focussing, these minute dots 

 disappear, and appear to be the depressions taken by Prinz for per- 

 forations. In C. gigas there are found also in the middle only small 

 round depressions which are surrounded towards the margin by a net- 

 work jirojecting outwards, so that this species has internally the struc- 

 ture of the punctured forms, externally that of G. oculus-iridis, radiatus, 

 and similar species. In Trinacria regina the depressions always 

 penetrate very deep, as is the case in many diatoms ; but at the base 

 of the depressions is a smaller indentation which, when highly mag- 

 nified, is very clearly seen in the middle of the pore, as occurs again 

 in many diatoms. Grunow has examined a large specimen of this 

 species, in which a further much more delicate and narrower puncta- 

 tion was visible, apparently on the inner surface of the valves. The 

 transverse section which Prinz draws of C. excentricus (or more 

 probably of C. symholophora) appears, however, to be correct ; and the 

 pore canals are here mostly represented as not completely reaching 

 the inner surface of the valve. If these depressions permit endosmose 

 through them, their thin inner wall can be perforated only by canals 

 so delicate that they are invisible to the highest powers. Grunow 

 promises a treatise on this difficult subject. 



Fineness of Striation as a Specific Character of Diatoms.* — 

 Prof. H. L. Smith comments upon the paper of Count Castracane on 

 this subject,! in which, it will be remembered, he arrived at the 

 conclusion that " the striee and their fineness are a quality of specific 

 importance." 



Prof. Smith says : — " In a few words appended to the translation 

 of the paper, Mr. Kitton, the well-known English diatomist, criticises 

 Coimt Castracane's conclusions, and indicates the mistakes of the 

 Count himself in his attempt to make these measurements, which he 

 deems of specific performance. The conclusion of the Count, how- 

 ever, will be heartily welcomed by ' species-mongers,' inasmuch as 

 one need have little fear in being able to sustain the claim to n. sp. if 

 allowed to fall back on striation as the test, for who shall decide ? 

 Not every one has at command the elaborate apparatus used by Count 

 Castracane for determining the number of stride. Photographs of 

 each diatom, projections on a large scale, &c., seem to be con- 

 sidered by him as the only trustworthy method ; a method of such 

 exactness that it ' enables him to disagree with microscopists of in- 

 contestable authority.' For Count Castracane personally, and as a 

 correspondent and a thoroughly conscientious, hard-working diatom 

 student, I have the highest respect, but I am sorry that he has felt 

 himself obliged to adopt so pernicious a view, as it seems to me. The 

 Diatomaceae belong to the vegetable world, and the principles governing 



* Amer. Mon. Micr. Journ., 11. (1881) pp. 221-3. 

 t See this Journal, i. (1881) p. 787. 



