1290 i General Notes. [December, 
S and Æ by means of a T-shaped tube, serves to catch any water 
which may find its way into the connecting-tube in consequence 
of variation in the water-pressure. The glass tube, mz, the lower 
end of which is in a bottle of mercury, serves as a manometer, 
The pressure indicated enables one to judge whether the prepar- 
ation is saturated with paraffine. 
In using this apparatus the water-bath, W, should be first heated 
to a temperature of about 60°; then the basin, P, containing melted 
paraffine and the object to be imbedded, may be placed in the ex- 
siccator and the pump set in operation. When the mercury 
reaches the highest point in the tube, 7, and air-bubbles cease to 
rise from the object, the process is ended, and the air admitted by 
loosening the screw-clamp, K. Before admitting the air, the stop- 
cock, Z, can be closed, in case it is thought best to leave the prep- 
aration still longer in vacuum. As soon as sufficient time has 
been given for complete saturation, the stop-cock, Z, is opened 
slowly, and the air streams in. he end of the connecting-tube 
is bent upward in Æ, in order that the paraffine may not be dis- 
turbed by the inflowing air. Finally, the object is taken out and 
placed in a box of melted paraffine and left to cool. 
With a water-pressure of 700—720 mm. Hg., most objects will 
. be completely saturated within 20 minutes. 
TREATMENT OF THE Ova AND EMBRYOS OF THE ApHIDES.—Wit- 
laczil ' gives a lengthy paper on the development of the aphides, 
and in it the following information on methods: Ape 
he embryos of the viviparous aphides were examined in a 
weak salt solution (1 ¥ percent), in which they live for about an hour. 
€ ovaries contain embryos in different stages of development, 
and have to be isolated for study. a 
The early stages in the development of the ova may be studied 
to advantage after treatment with hydrochloric acid (3 per cent), 
or acetic acid, as these reagents partially dissolve the yolk elements 
and thus render the preparation more transparent. The later stages, 
on the contrary, are rendered more opaque by the same treatme 
The ovaries of viviparous aphides were prepared for sectioning, 
by Ludwig Will,? in the following manner : a 
The aphis is killed in water heated to about 70° C., then hard- 
ened in successively higher grades of alcohol. In order to color 
in toto, the cuticula must be punctured with a sharp needle, 
then the dye will penetrate easily to all parts. As very thin see 
tions are required for the study of such small elements, it . sen 
to use dyes that stain very deeply, such as borax-carmine ee at 
matoxylin. It is further necessary to employ either the shellac or 
the collodion method of fixing the sections, otherwise the ine X = 
ant parts are liable to drop out of place. 
! Zeitschr. f. wiss. Zool., XL, Heft 4, p- 563-564. 
3 Semper’s Arbeiten, vI, 1883. 
ea pe ct a S SE = 
