314 ■ CHAPTER XXV. 



Vermes. 



639. Rotatoria.— Jennings {Dull. Mus. Harvard Coll., xxx, 

 1896, p. 101) finds the best fixative for pregnant females is 

 the strong liquid of FJemming, but the ova must then be 

 bleached with chlorate of potash (§ 575). 



Lenssen {La Celhile, xiv, 1898, p. 428) fixes ova of 

 ITydatina with sublimate for 20 seconds. 



640. Turbellaria.— Gardineu (Journ. of Morph., xi, 189.5, 

 p. 158) finds the best fixative for ova of Polychoeru.^ is a 

 mixture of equal parts of absolute alcohol and glacial acetic 

 acid. 



Bresslau {Zeit. iviss. ZooL, Ixxvi, 1904, p. 219) fixes 

 Mesostomidas with summer-eggs in Tellyesniczky's mixture 

 (either cold or warmed to 60° or 70° C.) for 10 to 12 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 suffi- 

 ciently shelled. 



Van dee Stkicht {Arch. Biol., xv, 1898, p. 370) finds that 

 ova of Thysaiiozooii will only cut well when they have been 

 not more than two minutes in absolute alcohol followed by 

 chloroform and paraffin as used by Garnoy and Lebrun, 

 § 603. 



See also, for Polyclads, Francotte, Arch. Zool. Exper., 

 vi, 1 898, p. 196 ; and, for fresh-water Planaria, Iijima, Zeit. 

 iciss. Zool., xl, 1881, p. 359. 



641. Cestoda (v. Beneden, Arch. Biol., ii, 1881, p. 187).— 

 Ova of Tsenia in which a chitinous membrane has formed 

 around the embryo ai-e 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 



