612 IN VERTEBRA TES 



alcohol with 10 per cent, of acetic acid. He stains with para- 

 carmine. 



1215. Crinoidea. Lo Bianco {loc. cit., p. 458) fixes Antedon 

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



1216. Larvae of Echinodermata (from instructions written down 

 for Lee by Dr. Barrois). For the study of the metamorphoses 

 of the Echinoidea and Ophiuridea it is necessary to obtain pre- 

 j^arations 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 the 

 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 larva 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 

 (§ 249). 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 Bipinnaria. 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. 



Larvce of Comatula are best fixed with liquid of Lang, and 

 stained with dilute borax carmine. It is important (for prepara- 

 tions that are not destined to be sectioned) to use only dilute borax 

 carmine, as the strong solution produces an overstain that cannot 

 easily be reduced. 



Narcotisation by chloral hydrate before fixing is useful, especi- 

 ally for the study of Pentacrinus larvae and of the young Synaptce 

 formed from Auricularia. Without this precaution you generally 

 get preparations of larvse either shut up {Pentacrinus), or entirely 

 deformed by contraction (young Synaptce). 



See also MacBridk on the development of Amphiurn squamata. 

 Quart. Journ. Micr. Sci., xxxiv, 1892, p. 131 (osmic acid followed by 

 liquid of Miiller and alcohol ; decalcification with nitric acid in alcohol ; 

 staining with Mayer's paracarmine or haemaluni) ; and Seeliger on 

 the development of Antedon, Zool. Jahrb., Ahth. Anal., vi, 1892, p. 161. 



MacBride {Quart. Journ. Micr. Sci., xxxviii, 1896, p. 340) fixes larvae 

 of Asterina in osmic acid, brings into liquid of Miiller for twelve to four- 

 teen hours, imbeds in celloidin followed by paraffin (see § 190), and 

 stains sections with carnialum or Delafield's hajmatoxylin, best after a 

 foregoing stain of twenty-four hours in borax carmine. 



Mayer {Grundziige, Lee and Mayer, 1910, p. 486) arranges a 

 number of fixed and stained Plutei on a sheet of gelatin foil 



