47 
SUMMARY OF CURRENT RESEARCHES 
RELATING TO 
ZOOLOGY AND BOTANY 
(PRINCIPALLY INYERTEBRATA AND CRYPTOGAMIA), 
MICROSCOPY, Etc.* 
ZOOLOGY. 
VERTEBRATA. 
a. Embryology, Evolution, Heredity, Reproduction, 
and Allied Subjects. 
Spermatogenesis of Opossum. — Theophilus S. Painter (« Journ . 
Exy. Zool ., 1922, 35 , 13-38, 3 pis., 8 figs.). There are 22 chromo- 
somes in the spermatogonia of Didelphys virginiana. The two smallest 
of these constitute a typical X-Y sex-chromosome complex, which can 
be followed through the growth period of the first spermatocyte. In 
the first maturation spindle there are 11 chromosomes — 10 tetrads and 
the X-Y chromosome. The X and Y components segregate from each 
other in this division so that the secondary spermatocytes contain either 
10 autosomes plus X, or 10 autosomes plus Y. There are 11 chromo- 
somes in all secondary spermatocytes ; one of these is either the X-com- 
ponent or the Y-component. In either case the sex-chromosome divides 
equationally. Half the sperms carry the X-chromosome and half the 
Y-chromosome. A study of dividing somatic cells of embryos showed 
that in both males and females 22 chromosomes were present. In the 
males the X-Y condition was found, in the females the 2-Y condition. 
J. A. T. 
Persistent Spermatogenetic Activity in Man. — P. Lecene 
{Comptes Rendus Soc. Biol ., 1920, 83 , 830-1, 1 fig.). In two cases of 
72 and 78 years the seminiferous tubules showed active spermatogenesis, 
and there were spermatozoa in the lumen. In a case of 67 years, 
however, the spermatogenesis had disappeared completely, and the 
seminiferous tubules had thick walls, with undifferentiated vesicular 
cells showing inactive nuclei. In all three cases the interstitial cells of 
* The Society does not hold itself responsible for the views of the authors 
of the papers abstracted. The object of this part of the Journal is to present 
a summary of the papers as actually published, and to describe and illustrate 
Instruments, Apparatus, etc., which are either new or have not been previously 
described in this country. 
