ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 731 



satisfactory results except for the more mature stages of the resting 

 spores, when it became necessary to use hot sublimate-acetic. 



Flemming's weaker solution was also tried, but though not superior 

 to the chrom-acetic mixture, gave excellent preparations after an im- 

 mersion of some weeks. Paraffin sections of the hosts infected with the 

 fungus were stained with safranin-gentian-violet. Heidenhain's iron- 

 haematoxylin was a failure. 



Studying the Histogenesis of the Retina.*— A. W. Weysse and 

 W. S. Burgess tried several fixatives with varying degrees of success. 

 Kleinenberg's picro-sulphuric mixture proved satisfactory, but the best 

 results were obtained from 70 p.c. alcohol DO ; glacial acetic acid 3 ; 

 formalin 7. In this the embryos remained for one week, and were then 

 transferred to 70 p.c. alcohol. 



The eyes were dissected out, cut in halves by a vertical section 

 through the optical axis, and placed in 90 p.c. alcohol for 3 hours, 

 followed by 1)5 p.c. alcohol for from 6-12 hours, according to size. 

 They were then cleared in cedar-oil, and imbedded in paraffin. The 

 sections were stained either with a 33 p.c. aqueous solution of Delafield's 

 hematoxylin followed by eosin, or by iron-alum followed by eosin. In 

 the latter case, the slide was first placed in a 4 p.c. aqueous solution of 

 iron-alum for 10 minutes. It was then thoroughly washed in tap-water, 

 dipped in a saturated aqueous solution of haematoxylin for 10 minutes, 

 and then again washed in water. This left the sections black. The 

 slide was then placed once more in the iron-alum solution, and carefully 

 watched until the sections were of a light purple tint. They were then 

 rinsed in water, and examined under the Microscope. 



If overstained, they were bleached a little longer in the iron-alum ; 

 if not stained enough, the hematoxylin was repeated. The slide was 

 next placed in an alcoholic solution of eosin for about 15 seconds, and 

 the excess of stain washed out in alcohol. 



Studying the G-astrulation of the Horned Toad, Phrynosoma 

 cornutum.t — C L. Edwards and C. W. Hahn found that in order to 

 obtain the earlier stages, it is necessary to take the eggs from the oviduct 

 of the gravid female immediately after it has been chloroformed. The 

 oblong eggs are cream-coloured, and when dry the shell becomes tough, 

 but not brittle or stiff. To fix the embryos free from yolk and separated 

 from the eggshell, a disk somewhat larger than the embryonic area was 

 cut out. In removing this a considerable portion of the yolk immediately 

 beneath was carried with it to sustain the embryo until it could be sup- 

 ported on all sides by physiological salt solution. By the use of a 

 current from a pipette the yolk was removed and then the shell mem- 

 brane and the vitelline membrane. Sometimes in very early stages 

 it was found desirable to allow the shell-membrane to remain on the 

 blastoderm for its support. 



Usually a drawing of the unstained embryo was made under a 

 magnification of 60 diameters in order to facilitate the interpretation of 

 sections. 



In general, Flemming's chrom-acetic-osmic acid followed by succes- 



* Amer. Nat., xl. (1906) pp. 611-37 (17 figs.). 



t Amer. Journ. Anat., v. (1906) pp. 331-51 (15 figs.). 



