440 SOME ZOOLOGICAL METHODS. 



Alcoholic picro-sulphuric acid may be indicated for fixing in 

 some cases. 



Some forms are very satisfactorily fixed with sublimate. 

 Such are the Copepoda and the larvae of Decapoda. It is 

 sometimes indicated to use the sublimate in alcoholic solution. 

 Some Copepoda, however (Copilia, Sapphirina), are better 

 preserved 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. The 

 pyrogallic process ( 233) may often prove helpful in the 

 study of such forms. 



823, 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 

 reagents has been described above, 557. 



LIST (Zeit. f. wiss. Mik., 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 may 

 stain before imbedding, with alum-carmine or picro-carmine 

 (five to six days) . 



The same methods are applicable to the preparation of the 

 ovaof Insecta forinstance, Periplaneta (see MORGAN, Am. Hon. 

 Mic.'Journ., ix, 1888, p. 234). 



824. Other Depigmentation Methods. Besides the depig- 

 mentation processes discussed in Chap. XXI Y, the following 

 methods are available. 



SAZEPIN'S Method for Antennae of Chilognatha (Mem. Acad. 

 Imp. St. Petersl., xxxii, 9, 1884, pp. 11, 12). Sazepin 

 treated antennas that have been dehydrated with alcohol by 

 steeping them in chloroform. The reaction is slow, the chitin 

 becomes gradually less opaque, but the pigment does not 

 entirely disappear. In order to remove the last trace of 

 it, it will be sufficient if a drop of fuming nitric acid be 

 now added to the chloroform. The mixture must be occa- 



