ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 545 



is approached, yet there are far more species known from the Atlantic 

 than from the Mediterranean. This is probably due to want of careful 

 research. He places the number of species at 31, as compared with 

 Ilaeckel's 18. Lists of the species are given, and certain new forms 

 are figured and described. 



New Infusorians.* — N. M. Stevens describes as Licnophora macfar- 

 landi sp. n., and Boveria subcylindrica g. et sp. u., two Infusorians 

 found within the respiratory tree of Holothuria calif oruica. Both occur 

 attached to the lining membrane of the tree, but there is no evidence 

 that they are injurious; both apparently feed on particles in the in- 

 coming water, or on waste material furnished by the host. Conjugation 

 was not observed in either case, but lateral or oblique fission occurs. 

 Prior to division the mouth and peristomial spire seem to atrophy, and 

 later reappear in the daughter-cells. 



Cell-division in Polytoma.f — S. Prowazek has studied the nuclear 

 changes during division in Polytoma uvella. Usually repeated divisions 

 take place within the external pellicle, so that 8 daughter-cells are 

 formed ; but as the dividing-energy begins to diminish, the number falls 

 to 4 or 2. The resting nucleus is rounded, and contains a deeply- 

 staining internal body, which the author prefers to designate only by a 

 general title. Connected by a thread with this central body is a 

 minute corpuscle, which, as division begins, travels out of the nucleus 

 and divides. In the cytoplasm it becomes surrounded by a clear area, 

 but the later stages are difficult to follow. The nucleus elongates, and 

 then displays a spindle, division occurring by the indirect method. The 

 body mentioned above, which migrates from the nucleus, must be re- 

 garded as a centrosome. 



Genus Dinobryon. — J. Brunnthaler | gives descriptions of all those 

 species of this genus which form colonies, comprising the sub-genus 

 Eudinobryon Lauterborn. He gives keys and tables, notes on distribu- 

 tion, and figures of several of the species. 



E. LeinmermannJ writing on the same subject, gives descriptions of 

 the sub-genera Epipyxis, Dinobryopsis, Eudinobryon, their species and 

 varieties, with a general discussion of distribution, a historical survey, 

 and a general account of the structure, habits, and life-history. The 

 investment gives a definite cellulose reaction, and contains within it 

 a very delicate cell which is more or less contractile, and is narrowed 

 posteriorly or drawn out into a stalk. Anteriorly it bears two flagclla ; 

 the nucleus is usually central, and the cell contains two chromatophores. 

 Reproduction takes place by longitudinal division, and as the chroma- 

 tophores do not split, each cell contains only one ; one only of the new 

 cells has an eye-spot. Another form of reproduction is by the forma- 

 tion of resting spores. 



Peridiniese of Norwegian Lakes.|] — H. Huitfeldt-Kaas finds that 

 the Norwegian lakes contain five species of Peridinieae, as contrasted 



* Proc. Cal. Acad. Sci. Zool., iii. (1901) pp. 1-42 (6 pis.). 

 t Oesterreich. Bot. Zeitschr., li. (1901) pp. 51-60 (1 pi.). 

 I Verhandl. Zonl.-bot. Ges. Wien, li. (1901) pp. 293-306 (5 figs.). 

 § Ber. Deutach. Bot. Ges., xviii. (1901) pp. 500-24 (2 pis.). 

 || Videnskab. Skrift. Christiania, i. (1900) 8 pp. and 1 pi. See also Bot. Cen- 

 tralbl, lxxxv. (1901) pp. 241-2. 



