EMBRYOLOGICAL METHODS. 355 



EISIG (Mitth. Zool. 8 tat. Neapel, xiii, 1898, p. 89) fixes 

 ova and larvge of Capitella with a freshly prepared mixture 

 of 3 parts 5 per cent, solution of sublimate in sea water and 

 1 part glacial acetic acid ; if necessary they may be first 

 narcotised with 2 per cent, solution of cocaine in sea water 

 (the precipitate produced by the sublimate dissolves after- 

 wards in alcohol). Then successive alcohols. He stains with 

 heemacalcium (with 5 per cent, acetic acid instead of 2 per 

 cent.), and washes out by prolonged treatment with alcohol 

 containing 2 per cent, of nitrate of aluminium. 



640. Rotatoria. JENNINGS (Bull. MILS. Harvard Coll., xxx, 

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

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

 bleached with chlorate of potash ( 575). He preserves in 

 80 per cent, alcohol, or in a mixture of equal parts of alcohol, 

 water, and glycerin. He dissects out the ova under the 

 microscope, and brings them into glycerin under a cover 

 supported on capillary glass tubes so as to allow of rolling 

 the eggs. 



641. Turbellaria. GARDINER (Journ. of Morph., xi, 1895, 

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

 mixture of equal parts of absolute alcohol and glacial acetic 

 acid. 



Method of IIJIMA (Zeit. f. wiss. Zool., xl, 1884, p. 359). 

 The capsule containing the ova (of fresh-water Planaria) is 

 opened with needles on a slide, in a drop of 2 per cent, nitric 

 acid. The ova are extracted and covered (the cover being 

 supported by paper or by wax feet). After half an hour 

 they are treated with successive alcohols under the cover, 

 and finally mounted in glycerin. For sections, the whole of 

 the contents of a capsule is hardened in the mass in 1 per 

 cent, chromic acid and cut together. 



642. Cestoda (v. BENEDEN, Arch, de Biol., ii, 1881, p. 187).- 

 Ova of Tseiiia 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. 



