ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 115 



vise to considerable difficulties. If the contents are in the fresh condition, 

 they burst out and become completely disorganised when the thick shell 

 is broken through. If hardened in the ordinary way, the yolk becomes 

 exceedingly hard and brittle. W. A. Haswell has overcome these diffi- 

 culties in the following way : The eggs are fixed with sublimate alcohol 

 followed by iodised alcohol and 90 p.c. alcohol. After hardening, they 

 are transferred to a solution of hypochlorite of soda. This trans- 

 ference is effected gradually through downwardly graded alcohols. If 

 this be done too rapidly, the shell will split. 



When the solvent action of the hypochlorite upon the cells has 

 proceeded far enough, the eggs are washed in distilled water and de- 

 hydrated in alcohol. From absolute alcohol, they are transferred to a 

 mixture of equal parts of absolute alcohol and anhydrous ether for 

 twenty-four hours. They then remain for a like period in h p.c solution 

 of photoxylin or celloidin in equal parts of absolute alcohol and ether, 

 followed by a 2h p.c. solution of the same. The celloidin blocks, 

 hardened in chloroform, are then finally imbedded in the hardest paraffin 

 in the usual way. 



(3) Cutting:, including- Imbedding- and Microtomes. 



Studying the Development of Amphioxus.* — The material at the dis- 

 posal of E. W. MacBride for this research consisted of a large number of 

 eggs, embryos at all stages, from the spherical blastula up to the pericd 

 when the mouth, club-shaped gland, and one gill-slit have been formed, 

 and a number of older larvae. The material was preserved for the most 

 part in corrosive sublimate and in osmic acid. The author considers 

 ■that osmic acid is beyond comparison the best reagent for the preserva- 

 tion of histological detail. When yolk is abundant, osmic acid makes 

 the material very brittle, so that for studying the stages of gastrulation, 

 material preserved in picrosulphuric acid and in corrosive sublimate 

 and acetic acid was used. But osmic acid material was exclusively em- 

 ployed in all later stages. 



For imbedding the embryos, MacBride used the following modifica- 

 tion of the celloidin and paraffin method : The celloidin containing the 

 embryos, after being congealed in chloroform, was transferred to cedar 

 oil. In this oil it became as clear as glass, so that the imbedded 

 embryo could be observed under the Microscope, and its orientation 

 determined. An appropriately shaped piece of celloidin was then cut 

 out and imbedded in paraffin. The sections were stained on the slide. 



Demonstrating Peripheral Nerve Terminations.! — R. C. Mullenix, 

 when studying the peripheral termination of the eighth cranial nerve in 

 Vertebrates, adopted Bielschowsky's method of impregnation. The 

 head of a recently killed fish was immersed in 12 p.c. formalin for at 

 least 24 hours ; the fixed material was next decalcified in 12 p.c. formalin 

 containing 1 p.c. nitric acid. After about 24 hours the acid was removed 

 by means of running water. The material was then transferred to 2 p.c. 

 silver nitrate for 24 hours or so, after which it w 7 as removed to an 



* Quart. Journ. Micr. Sci., liv. (1909) pp. 290-1. 

 t Bull. Mus. Comp. Zool. Harvard, liii. (1909) pp. 215-50 (6 pis.). 



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