FOR ZOOI.OCICAI, HUKPOSES. 1 27 



Tunicata. — Appendicularia should be placed for five minutes 

 in the chrom osmic mixture. 



Clavellina and Perophora are placed in chloral hydrate i per 

 thousand for six to twelve hours, and then killed with the mixture 

 often parts chromic acid i per cent, to loo parts [)ure acetic acid. 



Cio7ia ifiiestinalis is killed by adding the same mixture drop by 

 drop to the vessel of sea water in which it is expanded ; in about 

 half an hour it is dead, and it is then transferred to chromic acid, i 

 per cent., some of the same being injected into its interior with a 

 pipette, and after about half an hour it is transferred to weak 

 alcohol. 



Of the compound Ascidians, Botryllus is best killed by nar- 

 cotizing in chloral hydrate i per thousand, for an hour or two, and 

 then killing with a flood of hot solution of sublimate. 



Fishes. — Lo Bianco recommends both for Elasmobranchs and 

 Teleostei simple immersion in 70 per cent, alcohol, an incision being 

 made in the wall of the abdominal cavity, and the alcohol being 

 injected into the cavity and changed repeatedly. But I have found 

 that with Teleostei this method causes contraction of the tissues and 

 folds in the skin, and that cold solution of corrosive sublimate is a 

 much better reagent. After the fish have been in the sublimate 

 solution for half an hour to two hours they must be washed for 

 an hour or more in a current of fresh water and then transferred to 

 70 per cent, alcohol. Dog-fishes are best hardened in \ per cent, 

 solution of chromic acid for some hours, with injection into the body 

 cavity, then washed and transferred to alcohol. The colours of 

 Teleosteans are not preserved in spirit, but may be kept to some 

 extent in their original condition by placing the specimens after sub- 

 limate and washing, in glycerine and water, changing them constantly 

 into less diluted glycerine, and finally keeping them in pure glycerine- 

 The embryos of Elasmobranchs, skates, and dog fishes, may be 

 fixed either in sublimate solution for about fifteen minutes, or in 

 chromic acid i per cent., being washed in fresh water before they are 

 transferred to alcohol. 



GENERAL RULES TO BE OBSERVED. 



In practising the methods above described there are certain 

 principles which must be constantly remembered. Except in the 

 few cases where a greater strength is recommended, alcohol of the 



