EMBBYOLOGICAL METHODS. 309 



KosTANECKi and Wierzejski {Arch. mih. Avat., xlvii, 1896, 

 p. 313) lix the spawn of Pliysa foiitinalln either in 1^ to 2 

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

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

 cessive alcohols. They imbed entire ova in paraffin, but 

 isolated embryos in celloidin. 



622. Chiton, see Metcalf, Siud. Biol. Lab. Johns Hophins Univ., v, 

 1893, p. 251. (Ova with young embryos pvit for 20 to 45 seconds into 

 ecm de Labarnique, then into water, in which the chorion swells and can 

 easily be removed.) 



623. Lamsllibranohiatft. - Si'aupfacher [Jena Zeit., xxviii, 

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

 with hgemalum, and cuts in paraffin. 



LiLLiE [Ji.vrn. of Morph., x, 1895, p. 7) fixes ova of Unia 

 for ten to twenty minutes in liquid of Perenyi, a,nd preserves 

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

 of Merkel or sublimate, larvee with 0-05 to O'l per cent, 

 osmic acid, preserving them in glycerin. Glocliidia may be 

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

 be anaesthetised with chloral hydrate before fixing. 



Ai thropoda. 



624. Fixation of Ova. — In many cases the ova of Arthropods 

 are best fixed by heat (§ 13). This may be followed either 

 by alcohol or some watery hardening agent. If it be desired 

 to avoid heating, picro-nitric acid may be tried. 



625. Removal of Membranes. — It may often be advisable not 

 to attempt to remove them, but to soften them with eau de 

 Javelle or e,aii de Labarraque (see § 553). 



Morgan [Amer. Natural., xxii, 1888, p. 357) recommends 

 (for the ova of Periplaneta) eav, de Labarraque diluted with 

 five to eight volumes of water, and slightly warmed. Tin's 

 will soften the chitin membranes sufficiently in thirty to sixty 

 minutes, if employed before fixing. Fixed ova take longer. 

 The fluid must, of course, not be allowed to penetrate into 

 the interior of the ovum. 



626. Hbnking's Methods (Zeit. u-iss. Mik., viii, 1891, p. 

 15C). — Henkinq generally kills ova by plunging them into 

 hot water, or by pouring hot water on to them in a watch- 

 glass, and then removing into 70 jDer cent, alcohol. 



