CHAPTER XXV. 289 



midae with summer-eggs in Tellyesniczky's mixture (either cold or 

 warmed to 60 or 70 C.) for ten to twelve hours, and washes out 

 for the same time. He incises winter-ova at one pole, fixes and 

 brings into alcohol of 95 per cent., then makes an incision at the 

 other pole, and imbeds in paraffin through cedar oil. In the paraffin, 

 slices of the shell may be removed with a scalpel, and the ova re- 

 imbedded when sufficiently shelled. 



VAN DER STRICHT (Arch. BioL, xv, 1898, p. 370) finds that ova of 

 Thysanozoon will only cut well when they have been not more than 

 two minutes in absolute alcohol followed by chloroform and paraffin 

 as used by Carnoy and Lebrun, 602. 



See also, for Polyclads, FEANCOTTE, Arch. ZooL Exper., vi, 1898, 

 p. 196 ; and, for fresh-water Planaria, IIJIMA, Zeit. wiss. ZooL, 

 xl, 1884, p. 359. 



640. Cestoda (v. BENEDEN, Arch. Biol, ii, 1881, p. 187). Ova 

 of Tcenia in which a chitinous membrane has formed around the 

 embryo are impervious to reagents. They may be put on a slide 

 with a drop of some liquid and covered. Then, by withdrawing 

 the liquid by means of blotting-paper, the cover may be made to 

 gradually press on them so as to burst the membranes, and the 

 embryo may then be treated with the usual reagents. 



HASWELL (Quart. Journ. Micr. Sci., liv, 1909, p. 417) fixes ova of 

 Temnocephala in " sublimate alcohol," brings them into 90 per cent, 

 alcohol with iodine added, and thence gradually back into water, 

 softens the shells in weak sodium hypochlorite, washes and imbeds. 



641. Trematoda. COE (ZooL Jahrb., Abth. Morph., ix, 1896, 

 pp. 563, 566), for the special study of the excretory system of the 

 Miracidia of Distomum, kills with osmic acid, rinses with distilled 

 water, and puts for a couple of days into \ per cent, solution of 

 silver nitrate. 



Egg-capsules may be softened with 5 per cent, caustic potash 

 and then burst open (HECKERT, BibL ZooL, iv, 1889). 



642. Nematoda. The ova of Ascaris megalocephala, a classical 

 object of study, are one of the most impervious things in the animal 

 kingdom. Years ago FOL related to me that he had had ova seg- 

 menting right through absolute alcohol into balsam. BATAILLON 

 (Arch. Entwickelungsmech., 1901, p. 149) has had ova showing living 

 embryos after having been for six months in liquid of Flemming, 

 and found them to remain alive for months after drying for twenty- 

 four hours at 35 C., and mounting in balsam, and for weeks in acids 



or alkalies. 

 M. 19 



