Journal of Applied Microscopy. 



221 



from 1.44 to 1.60. The oil of cassia is cited 

 as being of especial value. It has a re- 

 fractive index of 1.601160, clears from 80 

 per cent, alcohol, and dries hard enough 

 to make permanent mounts. Following 

 is the table: 



Per cent, of 



Alcohol 

 which sub- 

 Refractive stance wUl 

 Index. dissolve. 



.80% 

 • 95% 

 .90% 

 .85% 



Linalool ' 1 .45941 . . 



Chloroform 1.4395 .. 



Oil Eucalyptus 1.46090.. 



Linaloe 1.46090.. 



Oil Pettigrains 1.46090 90% 



Oil Coriander 1.46288 33% 



Oil Peppermint 1.46327 85% 



Oil Cedar 1.46626 95% 



Oil Pinus Sylvestris ....1.46882..: 100% 



Turpentine 1.46882 100% 



Oil Lemon 1.47078 95% 



Oil Eucalyptus glob .... 1 . 47077 90% 



Oil Orange 1.47176 95% 



Oil Oinus Picea 1.47274 100% 



Oil Juniper Berries 1 . 47394 95% 



Oil Pinus Pimlionis 1.47620 100% 



Oil Citronella 1.47909 90% 



Oil Origanum 1.47919 95% 



Turpineol 1.48005 75% 



Oil Celery 1.48054 95% 



Oil Nutmeg 1.48054 95%. 



Oil Origanum 1.48103 95% 



Oil Caraway 1.48441 90% 



Oil Ginger 1.48807 95% 



Xylene 1.49348 95% 



Benzene 1.49488 95%, 



Carvol 1.49505 85% 



Oil Thyme 1.49638 95% 



Oil Copaiva 1.49723 Immisc 



Oil Cedarwood 1.50188 95% 



Oil Cedarwood 1.50326 95% 



Oil Cumin 1.50373 90% 



Oil Sandalwood (E. In.) 1.50510 90% 



Oil Calamus .1.50602 95% 



Oil Sandalwood (W. In) 1.50820 80% 



Oil Cedarwood 1.51533 95% 



Xylene Balsam 1.52397 



Oil Sassafras 1.52724 95% 



Oil Allspice 1.53062 85% 



Oil Cloves 1.53171 80% 



Oil Sweet Birch 1.53329 90% 



Oil Cinnamon leaves ..1.53535 85% 



Safrol (sp. gr. 1.108) ...1,53584 95% 



Oil Fennel 1.53885 95% 



Oil Cloves 1.53723 80% 



Oil Mirbane 1.54982 95% 



Oil Anise 1.55795 95% 



Oil Anethol 1.55208 90% 



Oil Anilin 1.58457 60% 



Oil Cassia 1.60160 80% 



E. M. Brace. 



The Microscope as Practically Applied to 

 Fish Culture. 



J. J. Stranahan. Read before the twenty-seventh 

 annual meeting of the American Fisheries So- 

 ciety, 1898, Omaha, Neb. 



The most important work of the micro- 

 scope in fish culture is, doubtless, to 

 determine the condition of eggs soon 

 after they are taken so as to remedy 

 early any errors of the spawn-taker 

 which may exist, and thus save unneces- 

 sary loss. 



In examining eggs under the micro- 

 scope, I use a cell that holds a certain 

 number of eggs, as for instance, in the 

 case of the whitefish my cell holds twenty 

 eggs in a row and five rows deep, making 

 in round numbers 100 eggs, although eggs 

 vary so much in size that this is not 

 absolute. 



The eggs which are impregnated, unim- 

 pregnated, and those with ruptured yolks 

 are so easily detected, one from the other, 

 that the cell may be moved under the 

 microscope as fast as one can count. 



It is the practice of the writer to 

 examine whitefish and cisco eggs twenty- 

 four hours after they are taken, when 

 segmentation is at its most distinct 

 period. The disc of the impregnated egg 

 will then be found divided into some fif- 

 teen or twenty cells, and very distinct, 

 under a half-inch objective. The disc of 

 the unimpregnated egg will be an almost 

 perfect hemisphere and will present a 

 much clearer appearance than the im- 

 pregnated one. The eggs with ruptured 

 yolks will present a varied appearance. 

 Generally the albumen will be in a layer 

 at the bottom, the oil globules at the top 

 and the disc, much distorted and out of 

 all semblance of the normal, floating 

 between the two. There is another class 

 of valueless eggs, those containing no 

 germinal disc at all, but they constitute 

 a very small per cent., and, of course, no 

 amount of care on the part of the spawn- 

 taker could put life into these, they need 

 not be taken into account at all. 



Thus, it will be seen, the eggs at the 

 station can be examined each day, each 

 lot separately, and a record of the work 

 of each and every spawn-taker kept, his 

 errors corrected or the man discharged, 

 and by going over the tables resulting 

 from this work, when about to engage 

 spawn-takers for a season, it can be seen 

 at a glance which are the best men, weed 

 out the poorer ones, and greatly improve 

 the spawn-taking force. 



About seventy-five spawn-takers are 

 employed at the Put-in-Bay station each 

 fall, and it will be apparent to the most 

 casual observer that this plan of examin- 

 ing eggs must result in the securing of a 

 much larger number of good eggs than 

 would otherwise be the case. 



The great advantage of the microscope 



