ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
839 
glycogen, but never starch ; the granulations are of two kinds, coarser 
and finer. There are no chromatophores, and the presence of a 
nucleus has not been determined with certainty ; in the normal state 
there are no vacuoles. 
The apical cell of the trichome, when this latter is uninjured, is 
distinguished from the rest by being clothed, in its apical portion, with 
a thicker membrane, which constitutes an organ of protection. It is 
separated from the rest of the trichome by a thin wall, and ceases to 
divide. The author proposes to term this thick membrane the calyptra. 
The form of the calyptra is characteristic of each species ; it is always 
intermediate between a cupola and a more or less sharp cone. The very 
delicate threads sometimes found attached to the apical cell are un- 
questionably parasites. 
The sheath is either mucous or cartilaginous. Its chemical reactions 
are different from those of the cell- wall, and approach more nearly those 
of cellulose, but it is insoluble in the cupro-ammoniacal solution. The 
cells never divide in a direction parallel to the axis, and there is conse- 
quently no true branching; but a false branching is the rule in the 
Yaginarieaa and in Plectonema ; it is terminal in the Yaginarieae, 
lateral in the Lyngbyese. 
The present paper is devoted to the Yaginarieae, which are included 
under 6 genera, viz. Schizothrix (including Inactis, Hypheothrix, 
Symplocastrum, and Chromosiphon) (27 species), Porphyrosiphon 
(1 species), Hydrocoleum (10 species, chiefly marine), Dasygloea 
(1 species), Sirocoleum (2 species), and Microcoleus (7 species). The 
following new species are described : — Schizothrix rubella , S. mexicana , 
S. Lenormandeana, S. Beccarii, S. Lamyi, S. Braunii, Hydrocoleum 
coccineum, Microcoleus acutirostris. 
Formation of Ooliths.* — Examining the calcareous stones from the 
shore of the Great Salt Lake in Utah, Dr. A. Rothpletz found them to be 
covered with a blue-green coating consisting of colonies of Glceocapsa and 
Gloeothece , which were excreting abundance of calcium carbonate. The 
lime is enclosed in the alga in roundish masses, and is a finely granular 
aggregate of calcite. These ooliths are undoubtedly the product of a 
lime-separating Schizophyte ; and the author believes this to be the 
case with the greater number of the marine calcareous ooliths with a 
regular zoned and radial structure, as also with the vermiform calcare- 
ous structures of the Sinaitic Peninsula. 
Rhizosoleniacese.t — Sig. H. Peragallo gives a monograph of this 
family of diatoms, comprising the genus Bhizosolenia and the allied 
genera Dactyliosolen , Lauderia, Attheya, and Guinardia gen. n. 
The family is divided into two sections, one with symmetrical, the 
other with unsymmetrical valves. To the former belong Dactyliosolen 
without spines but sometimes having a crown of marginal points, 
Lauderia with numerous more or less developed spines, and Attheya 
with two spines ; the latter section comprises Guinardia in which the 
valves have an undulating border with a rudimentary lateral mucro, 
* Bot. Centralbl., li. (1892) pp. 265-8. 
t Le Diatomiste, i. (1892) pp. 79-82, 99-117 (5 pis.). 
