September 8, 1922] 



SCIENCE 



287 



shown that both of these mammals possess the 

 X-Y type of sex chromosome. The sperma- 

 togenesis of the "ring-tail" monkey (exact 

 species not yet determined) shows essentially 

 the same conditions as were found in the opos- 

 sum and in man. 



In dividing spermatogonia (fig. 1) one 

 counts 54 chromosomes. It is to be noted that 

 the smallest element has no mate of like size 

 and shape. It is the "male determining," or 

 "Y" chromosome. 



During the first maturation division one finds 

 among the tetrads an element the two com- 

 ponents of which are very unequal in size 

 (fig. 2). This is the X-Y sex chromosome 

 complex. The X and the Y components go 

 undivided to opposite poles of the cell, so that 

 the secondary spermatocytes have either an 

 X or a Y chromosome. In the second matura- 

 tion division the sex chromosome (either X or 

 Y) divides equationally. 27 chromosomes have 

 been counted in the late telophase of the sec- 

 ond maturation division. (In figs. 2 and 3 

 only part of the tetrads are shown). 



In figure 4 the sex chromosomes — as seen 

 in the first maturation division — are given for 

 A opossum, B monkey, C man. It is inter- 

 esting to note that recent work on the genetics 

 of man (Sehoenfield — See Castle, Science, 

 Vol. 55, p. 703) confirms the results of my 

 cytological studies. 



Theophilus S. Painter 



University of Texas 



A SIMPLE GAS GENERATOR FOR 

 LABORATORY USE 



It is frequently necessary to prepare small 

 quantities of carbon dioxide, hydrogen, hydro- 

 gen sulfide, chlorine, hydrochloric acid gas, 

 oxygen, etc., in the general laboratory work and 

 in many laboratories it is not practicable nor 

 desirable to maintain a lot of elaborate equip- 

 ment for the generation of these various gases, 

 especially for the small quantities intermit- 

 tently needed. 



To prepare a special flask each time occasion 

 arises to generate a gas is at least bothersome 

 and time consuming and involves a waste of 

 reagents. On the other hand, a simple piece 

 of apparatus, taking no more room on the shelf 

 than a reagent bottle, adaptable to the prepara- 

 tion of any of several gases at a moment's 

 notice without waste of reagent, commends 

 itself. 



The apparatus here presented developed from 

 such a need and can be easily prepared out of 

 ordinary laboratory equipment; a large wide- 

 mouthed bottle, two test tubes, two cocks, 

 rubber stoppers and glass tubing are all that 

 is required. 



An examination of the diagram will show 

 the simplicity and convenience of construction 

 and operation. 



CONSTRUCTION 



Into the wide mouthed bottle A is fitted a 

 large rubber stopper D-D containing one small 

 hole for the tube E terminating in stopcock N, 

 and a large hole for the large test tube B. At 



