used for the killing. 



Cyclos tomans, Selachians, and Ganoids. — Small specimens 

 are put at once into 70 per cent alcohol. With large specimens 

 it is difficult for the alcohol to penetrate the viscera, and 

 it is necessary to make an incision in the belly, or else to in- 

 ject 90 per cent alcohol through the anus repeatedly and at every 

 change of fluid. 



Certain species of soft consistency, like Torpedo, are 

 better fixed if they are allowed to lie in 1 per cent chromic 

 acid for a half hour before they are put into alcohol. 



Embryos of Selachians (from 1 to 10 c. m. in length) are 

 fixed in saturated sublimate, where they may remain from five to 

 fifteen minutes. Be careful to wash well and to make use of the 

 usual test with iodine. When prepared thus they are also good for 

 histological studies. Fair success has attended the treatment of 

 the embryos of Torpedo, with the entire yolk sac attached, by plac- 

 ing them for fifteen minutes, in a mixture consisting of 1 per cent 

 chromic acid and saturated sublimate in equal parts, then washing 

 them in fresh water and putting them into alcohol. 



If it is desired to preserve moderately large Selachians 

 for the future preparation of the skeleton as well as the skin, 

 it suffices to open the belly, remove the intestines, and immerse 

 the animal in a 10 per cent solution of common salt. 



The Teleosts are treated like the Selachians, but the alco- 

 hol penetrates the tissues with still greater difficulty, and it 

 is necessary, particularly with the larger forms, to make repeated 

 injections of the liquid. The Teleosts with silvery skin (Trachy- 

 pterus) are put into saturated sublimate for a few minutes before 

 they are placed in alcohol. The transparent larval forms may be 

 put directly into weak alcohol, or may be fixed first with saturated 

 sublimate. 



The transparent fertilized eggs can be preserved for purpose 

 of demonstration by allowing them to remain for some minutes in the 

 mixture of alcohol and hydrochloric acid and then transferring 

 them to pure alcohol. 



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