ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 97 



Thallophyta. 



Algae. 

 (By Mrs. E. S. Gepp.) 



Growth and Scissiparity among the Peridiniese.* — Pavillard has 

 come to the conckision, after a study of the Peridiniese, that there exists 

 no authentic secondary growth among the symmetric species. The 

 formation of intercalary zones is a morphological preparation for cellular 

 division. Cellular division re-establishes the normal specific type, of 

 which the megacytic individuals, predestined to scissiparity, represent 

 a deviation. The general aspect of the phenomenon offers a curious 

 analogy to the ausosporalation of Diatoms. But the author does not 

 consider that this renders very close the affinity between Peridiniese and 

 Diatoms. Phalacliroma vastum, found and figured by Schtitt in a state 

 of division, represents the megacytic form of a species, the normal 

 organization of which corresponds to the soi-distant var. acuta, of the 

 same author. Phalacliroma Rudgei Murr. & Whit., furnished with 

 broad flat suture-plates, evidently constitutes the megacytic condition of 

 a species, of which the specific type remains unknown. 



Eye-spot of Algas and Flagellatae.f — W. Rothert, who has studied 

 the chromoplast of higher plants, has come to the conclusion that the 

 eye-spot of algge and flagellatae is nothing more than a chromoplast. 

 One is then dealing with an independent plasmic organ, which increases 

 always by division into two, and contains in a colourless stroma yellow 

 and red drops. The red and yellow colouring matter belongs to the 

 group of carotins, and is characterized by staining blue with sulphuric 

 acid. Certain facts which appear to conflict with the author's conclusion 

 can be explained satisfactorily. The chromoplasts of the Volvocine» 

 offer the greatest difficulties, since they are said to arise straight from 

 the cytoplasm. The whole question is, however, still unproved. 



Plankton of the Lietzensee.J— E. Kolkwitz wiiteson the causes of 

 the plankton development in the Lietzensee, near Charlottenberg. 

 Various alterations, dredging, embankment, etc., caused a production of 

 single-formed plankton, consisting in the warm seasons of the year 

 of OscilJatoria Agardhii, in the cold seasons of Stephanodiscus Hantz- 

 schianus var. pusilla. Both occurred in large quantities, especially 

 0. Agardhii. The alternation of these two species has remained constant 

 for seven years. On the bottom of the lake was formed a plentiful foul 

 mud, which smelt in places like tar and petroleum. Large quantities 

 of the plankton sank to the bottom and added to the mud. From the 

 sulphm- of the sinking Oscillatorise was formed sulphuretted hydrogen. 



' Comptes Rendus, clx. (1915) pp. 372-5. See also Bot. Centralbl., cxxix. 

 (1915), p. 5. 



t Ber. Deutsch. Bot. Gesell., xxxii. (1914) pp. 91-6. See also Bot. Centralbl. 

 cxxix. (1915) p. 440. 



% Ber. Deutsch. Bot. Gesell., xxxii. (1914) pp. 639-66. See also Bot. Cen- 

 tralbl., cxxix. (1915) p. 465-6. • 



Feb. 16th.. 1916 H 



