CHAPTER XXXVI. 



ME'l'HODS FOli INVElt'l'E];i;ATl«. 



Ttmicata. 



852. Fixation of Tunicata. — A method of Lo Biaxco* for 

 killing simple Asoidians in an extended state has been given^ 

 § 25. Some forms, such as Glavellina, Ptrophora, Phalhtsia, 

 Molgulu, Cynlhiu, etc., should first be narcotised by treat- 

 ment 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 jDrocess, followed by fixation with sublimate or 

 chromo-acetic acid. 



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

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

 30 CO. 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 Pyro- 

 soina. 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 



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

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



