METHODS FOE CLEARING AND SOFTENING CHITIN. 359_ 



Molluscoida. 



713 a. Bryozoa. For the methods of killing and fixing, 

 see 7, 14, and 15. 



Arthropoda. 



714. General Methods for Arthropoda, It may safely be 

 stated that, as general methods for the study of chitinous 

 structures, the methods worked out by Paul Mayer (see 4 

 and 5, and also 55 and 168) are superior to all others. It is 

 absolutely necessary that all processes of fixation, washing, 

 and staining should be done with fluids possessing great 

 penetrating power. Hence, picric-acid combinations should 

 be used for fixing, and alcoholic fluids for washing and 

 staining. Concentrated picro-sulphuric acid is the most gener- 

 ally useful fixative, 70 per cent, alcohol is the most useful 

 strength for washing out, and tincture of cochineal in alcohol 

 of 70 per cent. ( 168) is the most generally useful staining 

 fluid. Kleinenberg's hasmatoxylin may sometimes be prefer- 

 able, and alcoholic-carmine and borax-carmine will occasion- 

 ally give perfectly satisfactory results. 



Some forms are very satisfactorily fixed with sublimate. 

 Such are the Copepoda and the larvae of Decapoda. Some 

 Copepoda, however (Copilia, Sapphirina) , are better pre- 

 served by means of weak osmic acid, and so are the Ostra- 

 coda. In many cases the osmic acid will produce a sufficient 

 differentiation of the tissues, so that further staining may be 

 dispensed with ; Copilia and Phyllosoma are examples of forms 

 that may be prepared in this simple manner. 



715. Methods for Clearing and Softening Chitin. The employ- 

 ment of eau de Javelle or eau de Labarraque, as suggested by 

 Looss, for making chitin transparent and permeable to re- 

 agents has been described above 529. 



LIST (Zeit. f. wins. Hik., 1886, p. 212) has obtained good 

 results with Coccidae by treating them (after hardening) for 

 eighteen to twenty-four hours with eau de Javelle, diluted 

 with four volumes of water. After washing out with water, 

 the objects may be dehydrated with alcohol and imbedded in 

 paraffin, the chitin being sufficiently softened to allow of their 

 being penetrated and good sections being obtained. You 



