Cytologie und Befruchtung. — Descendenz und Hybriden. 7 



Es blieb nun Verf. somit nur noch als Ursache die Ueber- 

 arbeitung der Nervenzellen übrig, hervorgerufen durch eine ver- 

 grösserte Erregung, combinirt mit mangelnder Ernährung. 



Einige ähnliche aus der Litteratur angeführte Beispiele 

 machen dem Verf. wahrscheinlich, dass nur durch die letztge- 

 nannten Factoren eine irreparable Degeneration in dem be- 

 schriebenen Falle zu Stande kommt. Tischler (Heidelberg). 



Cannon, Wm. A., St u dies in Plant Hybrids: The 

 Spermatogenesis of Hybrid Cotton. (Bulletin of the 

 Torrey Botanical Club. Vol. XXX. March 1903. p. 133 

 — 172. Plates 7—8.) 



After reviewing earlier work on plant hybrids, giving 

 special attention to the work of Mendel, the writer considers 

 the cytological aspects of the subject. The hybrid cotton used 

 in the investigations was obtained by crossing Gossypium 

 barbadense X G. herbaceiim. The investigations deal 

 with the two mitotic divisions by which the micro- 

 spore mother-cell gives rise to the four microspores. In 

 practically all anthers of the hybrid cotton both normal and 

 abnormal conditions are present. In normal microspore mother- 

 cells the first nuclear division is heterotypic and the second 

 homotypic, and the two divisions are the exact homologues of 

 these divisions in pure races of plants. The two sizes of 

 chromatin rings or loops found in hybrid pigeons and in some 

 pure forms in plants were not found in the hybrid cotton. 



The behavior of the chromatin at the first division could 

 not be traced with sufficient accuracy to determine whether the 

 two daughter nuclei are of pure or of mixed descent. If 

 paternal and maternal chromatin is segregated as a result of 

 the two mitoses in microspore mothercells so as to form 

 nuclei with unisexual chromatin, such an Organization of the 

 chromatin would form a morphological basis for Variation in 

 accord with the Mendelian laws. 



Many abnormal cells were observed but these degenerate 

 before the first division of the microsporemother-cell. Amitosis 

 is not rare and is probably a factor which leads to infertility. 

 A few mother cells showed two spindles, as described by other 

 writers on hybrids, but in the hybrid cotton such cells degene- 

 rate before the first division is completed. 



Charles J. Chamberlain (Chicago). 



Pearson, Karl, On the Fundamental Conceptions of 

 Biology. (Biometrika. Vol. I. Part III. 1902. p. 320 

 —345.) 



This paper is a reply to Bateson's critism of the author's 

 memoir on Homotyposis. 



The author begins by criticizing the ill-defined way in 

 which B a t e s o n uses the terms, Variation, Discontinuity 



