METHODS Foil INVlfiUTEBRATES. 469 



Lo BcANCO kills small forms with weak alcohol, Ophiwpsila 

 with absolute alcohol, and Ophiomyxa with 0'5 per cent, 

 chromic acid. 



Russo (Richerche Lab. Anat. Roma, iv, 1895, p. 157) fixes 

 Ophiothrix for an hour or two in 0"5 per cent, osraic acid 

 and then decalcifies in solution of Miiller for six to ten 

 days. Or he fixes for three minutes in a mixture of two 

 parts concentrated sublimate solution, one part 70 per cent, 

 alcohol, and one part acetic acid (sp. gr. 106), and decalcifies 

 in Miiller or in 70 per cent, alcohol with 10 per cent, of 

 acetic acid. He stains with paracarmine. 



897. Crinoidea. — Lo Bjanco {loc cit., ]:>. 458) fixes Antedon 

 rosacea with 70 per cent, alcohol, A. phalangium with 90 

 per cent. 



898. Larvae of Echinodermata (from instructions written down 

 for me by Dr. Baeeois). — For the study of the metamor- 

 phoses of the Echinoidea and Ophiuridea it is necessary to 

 obtain preparations that show the calcareous skeleton preserved 

 intact (a point of considerable importance, since this skeleton 

 frequently affords landmarks of the greatest value), and that 

 give clear views of tlie region of formation of the young 

 Echinoderm (which is generally opaque in the living larva). 

 They should also possess sufficient stiffness to allow of the 

 larva being turned about in any desired way, and placed in 

 any position under the microscope. 



Pluteus larvas should be fixed in a cold saturated solution 

 of corrosive sublimate, for not more than two or three 

 minutes, then washed with water, and brought into dilute 

 Mayer's cochineal (§ 235). This should be so dilute as to 

 possess a barely perceptible tinge of colour. They should 

 remain in it for from twelve to twenty-four hours, being 

 carefully watched the while, and removed from it at the 

 right moment and mounted in balsam, or, which is frequently 

 better, in oil of cloves or cedar-wood. 



Auricularia and Dipinnaria. — As above, but the earlier 

 stages of the metamorphosis of Auricularia are better studied 

 by fixing with osmic acid, staining with Beale's carmine, and 

 mounting in glycerin. 



Larvae of Comatula are best fixed with liquid of Lang, 



