ZOOLOGY AND BOTANY, MICROSCOPY', ETC. 145 



tive are nomina nuda. A list of synonyms is given and a key to the 

 species. The many new forms of T. elh'pticus are represented on a 

 plate. 



Diatoms from the Province of Posen.* — V. Torka publishes a 

 list of 105 Diatoms collected in the streams of Brahe and Netze. Some 

 are new records for the Province. In the Xetze are found a considerable 

 number of halophil species, due to the fact that several tributariea 

 coming from the salt lands of Pinsk and Salzdorf empty themselves- 

 into it. 



Structure of the Nucleus in Algss and its Systematic Significa- 

 tion. f — H. V. Neuenstein writes a dissertation in which he reviews all 

 literature dealing with nuclear structure in alga3 except CyanophycejB, 

 and adds thereto a series of original observations made on numerous 

 algal nuclei, particularly Microspora amocna. His object was to 

 determine whether the arrangement and composition of the nuclear 

 elements, and especially the behaviour of the nucleus during division, 

 served as a trustworthy guide towards relationship. The systematic 

 position of doubtful genera could then be determined. His results were 

 as follows. On the whole the nuclear conditions are similar in I'elated 

 groups. At first sight it would seem as if there were no connexion 

 between nuclei and systematic grouping, for all sorts of nuclei are 

 represented, from karyosome nuclei to those which differ in no way 

 from those of the higher plants. The few forms having karyosome 

 nuclei must be regarded, however, as exceptions — Spirogyra, Sphseroplea 

 and the Nemalionales. The often-occurring centrosomes. particularly 

 in the Diatoms, recall animal objects. The number of the nuclei in 

 each cell is not so systematically important as the structure. The rule 

 is to be uninucleate. Exceptions are found in Confervales, where 

 most of the genera are uninucleate, wliile Ophiocytum and Boirydium 

 are multinucleate. For that reason Botrydium has lately been placed 

 in Siphonales. In Floridea^ uni-multinucleate plants of the same 

 species occur, the number of the nuclei increasing with the size of the 

 cell. However, the inclination to multiply nuclei with age is confined 

 to distinct groups. The author gives the special characteristics of the 

 separate families, which, however, are too long to reproduce here. 

 The results of the investigation show that cytology confirms the present 

 system of the algte. No new relationships have been established. But 

 it is proved that nuclear structure and the behaviour of the nucleus 

 during division and fertilization are not only advisable but necessary for 

 systematic purposes. 



Sapropelic Alg-ae.l — R. Lauterborn writes on the biology of the 

 foul mud found in natural waters, such as ponds or water-holes in woods, 



* Zeitschr. Deutsch. Ges. Kunst. u. Wiss. Posen, xxii. (1915) pp. 26-36 (3figs.). 

 See also Bot. Centralbl., cxxxii. (1916) p. 409. 



t Dissert. Heidelberg, 1914, 91 pp. (20 figs.). See also Bot. Centralbl., cxxxii. 

 (1916) pp. 432-3. 



: Ver. Nat. i\Ied. Vereins Heidelberg, n.f. xiii. (1915) pp. 395-481 (pis.). See 

 also Bot. Centralbl., cxxxii. (1916) pp. 401-3. 



Feb. '21st, 1917 L 



