240 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
by the fact that he has detected in these bodies a very delicate siliceous 
coat. 
Dr. r. Mi quel,* on the other hand, is unable to confirm the correct- 
ness of this statement in a very large number of cultures of diatoms, in 
which he has been able to follow out their life-history. The bodies 
within the cells of diatoms which have the appearance of spores, have, 
according to his experience, no power of germination. 
Nucleus of Diatoms.t — Dr. P. Miquel asserts that cell-division in 
diatoms is invariably preceded by a division of the nucleus. The best 
reagent for observing this he finds to be methylene-blue in an aqueous 
solution, either pure or slightly boric, which stains the nucleus a light 
violet-blue, while the stipe is coloured only with difficulty, and other 
spherical corpuscles of a different nature contained within the valves 
assume a dark blue or almost black tint. The nucleus is often rendered 
exceedingly difficult of observation by the phaeoleucites by which it is 
surrounded, or from its refrangibility being only slightly in excess of 
that of the surrounding protoplasm. Species specially favourable for its 
detection are Coscinodiscus concinnus and Biddulphia aurita. Dr. Miquel 
asserts that there is no intimate contact between the protoplasm and the 
enclosing siliceous valve. Whether the division of the nucleus takes 
place by karyokinesis or by simple fragmentation is still uncertain. It 
is only after the division of the nucleus has taken place that the cyto- 
plasm divides into two nearly equal portions. The nucleus is always 
surrounded by a mass of circumnuclear protoplasm, which differs in 
its reactions from the rest of the cytoplasm. 
New Genera of Diatoms.^ — Among a large number of new pelagic 
and fossil diatoms, Prof. J. Brun describes the following new genera : — 
Cotyledon. — Valve more or less circular, with an elevated crest, and 
irregularly folded. Near to Mastogonia and StepJianogonia. 
Hydrosilicon. — Valve lamellar (sometimes panduriform), bearing, 
both transversely and longitudinally, a pseudo-raphe with simple or 
double bifurcations towards the extreme curves of the valves; margin 
thick, ribbon-like, covered by a row of large pearls ; the centres of the 
radiation of the striae are the axes of crossing of the raphes. 
Radiopalma. — Frustule pellicular, with more or less regular orbicular 
outline ; ribs linear, running from the edges towards the centre, irregular 
in size and often dichotomous ; surface punctated or striated. 
Schmidt’s Atlas der Diatomaceen-Kunde. — The most recently 
published part (Heft 47) of this splendidly illustrated work consists of 
4 plates (185—8), almost entirely devoted to species of Mastogloia , 
with a few also belonging to Orthoneis and Dictyoneis. The author 
defines the genus Mastogloia as including those diatoms which have in 
the interior four free canals or double canals. 
Structure of the Cells of Phycochromaceae. — Herr G. Hieronymus § 
reaffirms his conclusions on several points respecting the structure of 
the cells of the PhycochromaceaB. The green pigment he believes to be 
connected with coloured granules or grana, while the blue pigment is 
* Tom. cit., pp. 26-9. t Ann. de Micrographie, v. (1893) pp. 437-61 (3 pie.). 
I Mem. Soc. Phvs. et Hist. Nat. Geneve, xxxi. (1893) 48 pp. and 12 pis. 
§ Bot. Ztg., li. (i893) l ,e AbtheiJ., pp. 73-80. Cf. this Journal, 1890, p. 371. 
