460 SOME ZOOLOGICAL METHODS. 



is apparently the best fixing agent. If any watery fluid be 

 preferred, care should at all events be taken to get the sponges 

 into strong alcohol as soon as possible after fixation, on account 

 of the rapidity with which maceration sets in in watery fluids. 

 FIEDLER (Zeit.f. wiss. ZooL, xlvii, 1888, p. 87) has been using 

 (for Spongilla), besides absolute alcohol, an alcoholic sublimate 

 solution, and the liquids of Kleinenberg and Flemming, with 

 good effect. 



Staining. On account of the great tendency to maceration 

 above referred to, I hold (notwithstanding many recommen- 

 dations of watery stains that are to be found in the literature 

 of the subject) that alcoholic stains be alone employed for 

 staining sponges, and I particularly recommend Mayer's tinc- 

 ture of cochineal as giving the best results personally known 

 to me. 



Sectioning. Calcareous sponges may be decalcified in alco- 

 hol slightly acidified with hydrochloric acid, and then im- 

 bedded in the usual way. Siliceous sponges may be desi- 

 licified by Mayer's hydrofluoric acid method mentioned ante, 

 574. But in view of the really dangerous nature of this 

 operation, I feel bound to recommend that it be avoided. 

 Fair sections may be obtained from sponge tissues well im- 

 bedded in paraffin without previous removal of the spicula. 

 The spicula appear to be cut ; probably they break very 

 sharply when touched by the knife. Of course you will not 

 use your best knives for cutting such sections. 



Preparation of Hard Parts. Siliceous spicules are easily 

 cleaned for mounting by treating them on a slide with hot 

 concentrated nitric or hydrochloric acid, or solution of potash, 

 or soda. The acids mentioned are very efficient, but it must 

 be pointed out that they will attack the silex of some delicate 

 spicules. Thus DEZSO found that the small stellate spicules 

 of the cortex of Tethya lyncurium are completely dissolved 

 by boiling hydrochloric acid. Potash solution is therefore 

 frequently to be preferred, notwithstanding that, in my expe- 

 rience, it does not give such clean preparations. 



According to NOLL, eau de Javelle is preferable to any of 

 these reagents (see 556). 



Impregnation with Silver (see 217). 



Larvae of Spongiae. SCHULTZE (Zeit. f. wiss. ZooL, xxxi, 

 p. 295) places the ova and larvae of Sycandra raphanus in 



