281 



SUMMAEY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICEOSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 



a, EmbryologY.t 



Chromosomes of Human Spermatocyte s4 — H. L. Wiemann finds 

 that the metaphase plates of human spermatogonia contain twenty-four 

 straight or bent rod-shaped chromosomes, two of which are presumably 

 idiochromosomes forming an XY-pair. Throughout the growth period 

 •of the primary spermatocyte, the idiochromosomes persist as a basic 

 staining bipartite body whose components are sometimes separated, in 

 which cose there are two chromatin nucleoli in the nucleus instead of a 

 single-paired one. 



In the prophase of the primary spermatocyte twelve bivalent 

 chromosomes appear, one of which is the XY-pair. The XY-pair 

 divides longitudinally in the primary spermatocyte division. The 

 remaining eleven bivalent chromosomes also divide in this division, but 

 whether quantitatively or qualitatively was not determined. An inter- 

 kinesis stage follows in which the nucleus contains a double chromatin 

 body resembling the chromatin nucleolus of the first spermatocyte. It 

 is suggested that this body is one-half of the longitudinally split XY-pair 

 of idiochromosomes which persist throughout the interkinesis stage. 



The second spermatocyte metaphase plates contain twelve chromo- 

 somes, one of which can be recognized as a half of the split XY-pair. 

 In the division it is assumed that the X- and Y- constituents pass 

 undivided to opposite poles, while the remaining eleven chromosomes all 



* The Society are not intended to be denoted by the editorial" we," and they 

 do not hold themselves responsible for the views of the authors of the papers 

 noted, nor for any claim to novelty or otherwise made by them. The object of 

 this part of the Journal is to present a summary of the papers as actually pub- 

 lished, and to describe and illustrate Instruments, Apparatus, etc., which are 

 either new or have not been previously described in this country. 



t This section includes not only papers relating to Embryology properly so 

 called, but also those dealing with Evolution, Development, Reproduction, and 

 allied subjects. 



X Amer. Journ. Anat., xxi. (1917) pp. 1-20 (4 pis.). 



June 20th, 1917 tj 



