CHAPTER XXXVI. 



METHODS FOR INVERTEBRATES. 



Tunicata. 



929. Fixation of Tunicata. A method of Lo BIANCO * for killing 

 simple Ascidians in an extended state has been given, 25. Some 

 forms, such as Clavellina, Perophora, Phallusia, Molgula, Cynthia, 

 etc., should first be narcotised by treatment for from three to twelve 

 hours with chloral hydrate (1 : 1000 in sea water), then killed in a 

 mixture containing chromic acid of 1 per cent. 10 parts, acetic acid 

 of 50 per cent. 100 parts, and finally hardened in 1 per cent, chromic 

 acid. 



The compound Ascidians with contractile zooids may be left in 

 clean sea water till the zooids have become fully extended, then 

 fixed by VAN BENEDEN'S acetic acid process, 84 (steel instruments 

 being avoided for manipulating them). I strongly recommend this 

 process. 



S. Lo BIANCO recommends for this group the chloral hydrate 

 process, followed by fixation with sublimate or chromo-acetic 

 acid. 



CAULLERY (Bull. Sc. France Belg., xxvii, 1895, p. 5) first stupefies the 

 animals with cocaine (LAHILLE, a few drops of 5 per cent, solution to 

 30 c.c. of sea water), then fixes in liquid of Flemming or acetic acid. 



Most small pelagic Tunicates are very easily fixed with osmic acid 

 or acid sublimate solution. 



I have found the acetic acid process very good for Pyrosoma. Lo 

 BIANCO puts them for a quarter of an hour into 50 per cent, alcohol 

 containing 5 per cent, of hydrochloric acid, then into successive 

 alcohols, beginning with 60 per cent. He kills the hard forms of 

 Salpa with acetic acid of 10 per cent., the semi-hard ones with 1 per 

 cent, chromic acid containing 5 per cent, acetic acid, the soft ones 

 with 1 per cent, chromic acid containing -^ per cent, osmic acid, or 

 10 parts of 1 per cent, chromic acid, with 1 of formol and 9 of sea 

 water, Doliolida3 with sublimate, or the above osmic mixture, or a 



* References to methods of Lo BIANCO in this Chapter are all to his 

 paper in Mitth. Zool. Stat. Neapel, ix, 1890, p. 435. 



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