E.MBRYOLOGICAL METHODS. 349 



p. 35). Or, preferably, the ova are put into salt solution, 

 the shell removed, the albumen removed with a pipette full 

 of salt solution, which dissolves it ; the ova are then fixed 

 for one minute in Pol's modification of liquid of Flemming, 

 and brought direct into Orth's picro-lithium-carmine. 



See also WASHBUBN, Amer. Nat., xxviii, 1894, p. 528 (liquid of Flem- 

 ming or 0*3 per cent, chromic acid, or 1 per cent, osmic acid, followed by 

 liquid of Merkel). 



CONKLIN (Journ. of Morph., xiii, 1897, p. 7) fixes ova of Crepidula for 

 fifteen to thirty minutes in picro-sulphuric acid, and stains with dilute 

 acidified haematoxylin of Delafield. 



KOSTANECKI and WIERZEJSKI (Arch. f. mik. Anat., xlvii, 

 1896, p. 313) fix the spawn of Physa fontinalis either in 1J 

 to 2 per cent, nitric acid, or in " sublimate and 3 per cent, 

 nitric acid in the proportion of 2 : 1," and bring through 

 successive alcohols. They imbed entire ova in paraffin, but 

 isolated embryos in celloidin. 



CARAZZI (Anat. Anz., xvii, 1900, p. 78) for Aplysia takes 

 5 per cent, sublimate with 2*5 per cent, glacial acetic acid. 



621. CHITON, see METCALF, Stud. Biol. Lab. Johns Hopkins Univ., v, 

 1893, p. 251, or Joum. Roy. Mic. Soc., 1894, p. 531. 



622. Lamellibranchiata. STAUP PACKER (Jena Zeit., xxviii, 

 1893, p. 196) fixes embryos of Cyclas in sublimate, stains 

 with haemalum, and cuts in paraffin. 



LILLIE (Journ. of Morph., x, 1895, p. 7) fixes ova of Unio 

 for ten to twenty minutes in liquid of Perenyi, and preserves 

 them in 70 per cent, alcohol, or advanced embryos with liquid 

 of Merkel or sublimate, larvae with 0'05 to O'l per cent, osmic 

 acid, preserving them in glycerin. Glochidia may be cut 

 with the shell in paraffin of 58 melting-point ; they may be 

 anaesthetised with chloral hydrate before fixing. 



Arthropoda. 



623. Fixation of Ova. In most cases the ova of Arthropods 

 are fixed by heat in a more satisfactory way than by any 

 other means. This may be followed either by alcohol or 

 some watery hardening agent. If it be desired to avoid 

 heating, picro-sulphuric acid may be tried. 



