No. 2, March, 1921] CYTOLOGY 105 



CYTOLOGY 



Gilbert M. Smith, Editor 

 Geo. S. Bryan, Assistant Editor 



719. Agar, W. E. Cytology, with special reference to the metazoan nucleus. XII + 

 224 p. MacMillan and Co. : London, 1920. $4.00. 



720. Bayliss, W. M. The properties of colloidal systems. IV. Reversible gelation in 

 living protoplasms. Proc. Roy. Soc. London B, 91:19&-20J.. 1920. — The author describes 

 use of intense dark ground illumination to reveal Brownian movement of minute particles 

 in apparently clear pseudopodia of Amoeba. He describes a temporary gelation of this 

 protoplasmic sol (cessation of Brownian movement) by suitable electrical stimulation, and 

 discusses subject in general. Plant cells, because of walls, are not so suitable for intense 

 dark ground illumination, but Nitella and stamen hairs of Tradescantia are fairlj^ satisfac- 

 tory. — Paul B. Sears. 



721. Don CASTER, L. An introduction to the study of cytology. 280 p., 24 pi., 31 fig. 

 University Press: Cambridge, 1920. $8.50. 



722. C, A. H. [Rev. of: Doncaster, L. An introduction to the study of cytology. 

 280 p., 24 pi., SI fig. University Press: Cambridge, 1920.] Jour. Bot. 58: 205-206. 1920. 



723. G., J. B. British cytology. [Rev. of: Doncaster, L. An introduction to the study 

 of cytology. XIV + 280 p., 24 pi. University Press: Cambridge, 1920.] Nature 105: 190- 

 191. 1920. "Not intended as a text book though it contains a wealth of facts; but its 

 aim is to interest the senior student by pointing out the way in which cytology is related to 

 the great fundamental problems at the root of all biological research. — 0. A. Stevens. 



724. Carter, Nellie. Studies on the chloroplasts of Desmids. IV. Ann. Botany 34: 

 301-319. 3 pi. 1920. — In this the last of a series of four articles on the chloroplasts of the 

 Desmidiaceae (See Bot. Absts. 4, Entry 166 and 6, Entry 1191) the structure of the chloroplast 

 of Staurastum is taken up. In sixteen of twenty-two species discussed there is a fairly massive 

 central axial chloroplast, typically with one pyrenoid, from which a more or less definite lobe 

 arises opposite each angle of the cell. This lobe is forked, and very often the forking is so 

 deep that the lobe appears as two masses or plates arising from the central axis of the chloro- 

 plast. Exceptional cases are found primarily in the larger species of the genus. Thus in 

 S. Ophiura Lund, the chloroplast lobes are between and not opposite the arms of the cell, 

 while in S. Arctiscon (Ehr.) Lund, there is only one projection into each arm of the cell. 

 Owing to the greater size of the lobes and reduction of the central mass in S. sexangulare 

 (Bulnh.) Lund, and S. anatinum Cke. & Wills, pyrenoids are not found in the central mass 

 but in the lobes. In S. grande Bulnh. the chloroplasts are parietal, although in very young 

 semi-cells there is a central mass. Another quite unusual arrangement is that found in 

 S. tumidum Breb., where there are from twelve to fifteen or more chloroplasts in the form of 

 narrow bands running through the semi-cell. — The final portion of the paper is devoted to a 

 discussion of chloroplast division in the whole family. In the Saccodermae, division of the 

 chloroplast starts before division of the nucleus. In the Placodermae, nuclear division is 

 completed and the new semi-cells have begun their development before there is any indi- 

 cation of chloroplast division. Division in this subfamily is not by constriction but by a 

 budding of the chloroplast into the new semi-cell until the chloroplast volume is the same in 

 the new and old semi-cells, when there is a division at the cell isthmus. At the time when 

 the chloroplast begins to grow into the new semi-cell the pyrenoid gives off a small bud which, 

 soon after its separation, grows in volume until it reaches the size of the original pyrenoid. 

 — Gilbert M. Smith. 



