354 SOME ZOOLOGICAL METHODS. 



CHAPTER XXXII. 



SOME ZOOLOGICAL METHODS. 



Tunicata. 



705. Fixation of Tunicata. The method of SALVATORE LO 

 BIANCO for killing Ascidians in an extended state has been 

 given above, 19. 



The compound Ascidians with contractile zooids are difficult 

 to manage if one does not go the right way to work. The 

 best process known to me is the following (due to VAN BENEDEN, 

 kindly communicated to me by Dr. C. Maurice). Place the 

 conns in clean sea water, and leave them alone for a few 

 hours, in order that the zooids may become fully extended. 

 Seize the corms with your fingers, and plunge them suddenly 

 into glacial acetic acid. Leave them there for two, four, or 

 six minutes, according to the size of the corms (which of 

 course you will have taken care to select of as small a size as 

 possible) . Take them out of the acid with your fingers (or in 

 some manner that may dispense with the employment of steel 

 instruments, which would blacken the tissues) and bring them 

 into 50 per cent, alcohol. Wash them thoroughly in that, and 

 then bring them in the usual way through successively stronger 

 alcohols. 



I most strongly recommend this process, which gives 

 admirably preserved preparations quite free from any opacity 

 either in the tissues or the tunic. The acid will not hurt the 

 fingers if they be washed immediately. 



Small pelagic tunicates are very easily fixed with osmic acid 

 "i- acid sublimate solution, with the exception of Anchiuin. 

 The not very numerous preparations I have made of this 

 exceedingly delicate form have all been unsatisfactory. And 

 some other similar forms may be found difficult. I have just 

 had a striking failure with Salpa virgula, which I fixed with 



