108 CYTOLOGY [BoT. Absts., Vol. VII, 



has more than two poles. The spindle figure is the visible morphological expression of invis- 

 ible currents of exchange passing between chromosomes and cytoplasm. The aster is a 

 similar expression of a metabolic current in the opposite direction, from the cytoplasm 

 toward the chromatic mass. The two currents meet at the poles of the cell, which are there- 

 fore regions of relative calm. If exchanges between chromosomes and cytoplasm cause a 

 deposition of a visible chemical substance, it accumulates at these regions; such deposits 

 are the centrosomes. If more material is deposited than is used by the cell during division, 

 the centrosome is a permanent organ; otherwise it is not. The centrosome is thus neither 

 exclusively cytoplasmic nor exclusively nuclear in origin, but comes from both as a precipi- 

 tation of substances resulting from the metabolic exchange between the two. Chemical 

 reactions, manifesting themselves in centrifugal currents of exchange between centrosome and 

 cytoplasm, cause the appearance of the attraction sphere. When the chromatic mass divides, 

 a second current of exchange is set up toward the centrosome, and a second centrosome is 

 deposited near the first; the assumption of centrosome division is not necessary to account 

 for the two. The formation of centrosomes seems to be conditioned by the size of the spindle 

 cone, the cone in turn being proportional to the chromatic mass under whose influence it 

 arises. The size of the centrosome is often observed to be proportional to that of the chro- 

 matic mass. The disposition and orientation of the chromatic masses determines the ori- 

 entation of the spindle, and the location and size of the centrosome. — Attention is called to 

 the relationship between centrosome and nucleolus. In some lower organisms a single 

 "nucleolocentrosome" performs the functions of both, whereas by a division of labor two 

 separate organs have become differentiated in most organisms. — L. W. Sharp. 



733. Ladreyt, F. La Cellule complexe symbiotique. [The symbiotic cell complex.] 

 Compt. Rend. Acad. Sci. Paris. 169: 665-667. 1919. — From a review of his own work and that 

 of others, the author concludes that the cell complex consists of various elements — the cyto- 

 plasm, nucleus, chondriosomes, etc. — which bear a symbiotic relation to one another and 

 derive benefit from one another. — V. H. Young. 



734. Meyer, Arthur. Morphologische und Physiologische Analyse der Zelle der Pflanzen 

 und Tiere. [Morphological and physiological analysis of the cell of plants and animals.] 



XX + 629 p., 205 fig. Gustav Fischer: Jena, 1920. (38 marks.) 



735. Rhumbler, L. Otto Biitschlis Wabentheorie. [Otto Biitschli's alveolar theory.] 

 Naturwissenschaf ten 8 : 549-555. 1920. 



736. Spek, Josef. tJber Biitschlis Erklarung der karyokinetischen Figur. [On Biit- 

 schli's explanation of the karyokinetic figure.] Naturvvissesnchaften 8: 561-562. 1920. 



737. Spek, Josef. Ueber physikalisch-chemische Erklaerungen der Veraenderungen der 

 Kernsubstanz. [Concerning physico-chemical explanations of the changes of the nuclear 

 substance.] Arch. Entwicklungsmech. 46: 537-546. 1920. This is mainly, though not exclu- 

 sively, a discussion of Paolo Della Valle's work entitled "La morfologia della cromatina 

 dal punto di vista fiscico" (Arch. Zool. Ital. 6: 37-321. 1912.) The general nature of the 

 nuclear substances, the number and size of chromosomes, susceptibility of chromosomes 

 to stains, division of chromosomes, individuality of chromosomes, and other similar subjects 

 are briefly considered by the author. — John H. Schaffner. 



738. Van Hoof, L. La spermatogenese dans les mammiferes. III. Les spermatocytes 

 leptotenes et amphitenes dans le Taureau. [Spermatogenesis in the mammals. III. The 

 lep to tene and amphitene spermatocytes in the bull.] La Cellule 30: 7-25 1 pi. 1915-1919. — 

 Author reexamines the "quaternary granulations" described by Schoenfeld (1901) in the 

 nuclei of the spermatocytes of the bull and finds them to be merely the symmetrically arranged 

 thickenings of the amphitene threads. In the nuclei of the spermatogonia and spermatocytes 

 the chromatin takes the form of irregular blocks with a few thin strands. In the heterotypic 

 prophase the leptotene threads develop at the expense of these blocks, vestiges of which may 



