228 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Yol-. IT. 



a longer stay in it the yolk-spherules blacken and the chromatin elements 

 in the nuclei are stainable with more difficulty in alum-hsematoxylin. 

 After the employment of any of the hardening reagents the larvae were 

 washed for a couple of minutes in distilled water, for ten minutes in 50°/ ^ 

 alcohol, then in 70° j ^ alcohol, until all traces of the hardening reagent 

 were removed, when they were put into and kept in 9S^!o alcohol. The 

 larvae were, as a rule, and more advantageously, stained hi toto in alum- 

 haematoxylin or alum-cochineal. When the sections, obtained after 

 imbedding by the chloroform-paraffin method, were fixed on the slide 

 with clove oil-collodion, a second stain, eosin, was, when desired, 

 employed. I used, also, the triple and quadruple stains of Gaule for 

 the larvae as well as for sections of the spleen in Nectiirus, but I cannot 

 say that I have derived any advantage from them. 



Cover-glass preparations were made of the blood of the larvce and of 

 Necturus. These were fixed either in the fumes of osinic acid [1°/ 

 solution for two hours ), or by a saturated solution of corrosive sublimate, 

 or picric acid, ax by Erlicki's Fluid. These were the only reagents which 

 I found serviceable. The method of operating was to decapitate the 

 living specimen, to allow a small drop of the blood to fall on the cover- 

 glass on which it was evenly spread, then to submerge the cover in 

 corrosive sublimate solution for five minutes, in picric solution for five 

 hours, or in Erlicki's fluid for two days. When osmic acid was used the 

 cover was put, with the preparation surface downward, on the mouth of 

 the unstoppered reagent bottle for two hours. The fixation was com- 

 pleted as usual with alcohol and the various dyes referred to above were 

 used for staining the preparations. 



Fresh cover-glass preparations of blood were also extensively studied 

 both before and after the addition of coloring reagents, such as acetic 

 methyl-green, acetic methyl-violet, picrocarmine, &c. 



As regards the optical apparatus, I had for the finer work the yV iii- 

 hom. imm. of Leitz, the yV in. horn. imm. (r43 N. A.) of Powell and 

 Lealand, the yi in. hom. imm. and the L. (water imm. -g-V in.) of Zeiss. 

 I used during the last summer the 3 mm. apochromatic of the last named 

 maker when studying the blood of the larval Auiblystomata. 



B. STRUCTURE OF THE BLOOD CORPUSCLES IN NECTURUS. 



The freshly drawn blood oi Necturus contain'^ the usual red corpuscles 

 of known form, leucocytes and the so-called fusiform corpuscles. The 

 first and last classes of elements merit a detailed description, owing 



