THE MICROTOMIST'S VADE-MECUM

water is largely used at the Villefranche Zoological Station      e
as a fixative and preservative for Ctenophora, Siphonophora,
and other Coelenterates, as well as for many other delicate
pelagic organisms.
631. Porifera (Dezs's method ').-Specimens of Tethya
lyncurium   (gemma) preserved in absolute alcohol were             ne
treated with 0-25 per cent. osmic acid, stained with neutral       t
carmine solution (Beale's formula), cleared, and imbedded in
paraffin for cutting. As regards skeletal parts, it should
be noted that Dezso found that the small stellate spicula of
the cortex are completely dissolved by boiling hydrochloric         t
acid. It seems to the present writer that the study of the        he
skeleton of siliceous sponges should always be controlled by thr&
sections mounted in balsam without being treated with either      they
acids or alkalies. And it should further be noted that such
sections should not be mounted in glycerin-jelly, which may
happen to have the same refractive index as the silex of the      s
spicula, in which case the latter will become perfectly invisible.
I have lost several slides in this way. Gum-water produces        at
the same effect.                                                    1
632. Porifera (Reniera semitubulosa) (Keller's methods 2).      lt
-The living sponge was treated with sea-water, gold and            i8
silver salts, and osmic acid of from Ath to fo-th per cent.        at
(The commonly employed I per cent. solution is much too            Al
strong.) Alcohol specimens were treated with picro-carmine, a
eosin, and ammonia-carmine. The best-preserved specimens
were obtained by means of osmic acid followed by weak
chromic acid. It is essential to the success of the silver-
process for demonstrating the pavement epithelium      of the
ectoderm that the surface of the sponge be perfectly clean.
633. Porifera (Embryology) (F. E. Schultze's methods ).-
For the study of the larve of Sycandra raphanus, Schultze
I ' Arch. Mik. Anat.,' xvi (1879), p. 627.
2 ' Zeit. wiss. Zool.,' xxx, p. 565.
3 Ibid., xxxi, p. 295.

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