ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 127 



from the deeper parts. ( 2) These are placed in absolute alcohol, which 

 is renewed several times for two days. 



Calcareous sponges.^ (3) Overstain with aqueous 1 per cent, solu- 

 tion of nigrosin (2 days or more). (4) Frequent washing in 90° alco- 

 hol (1-2 days). (5) Absolute alcohol, 1 day. (6) Absolute alcohol 

 and ether in equal bulks for 1/2-1 day. (7) Immersion in celloidin 

 for several days. (8) Imbed in celloidin, hardening with chloroform ■ 

 vapour. (9) Place the blocks in 80° alcohol. (10) Decalcify (1-2 clays) 

 in the following mixture : alcohol (90°) 100 parts, nitric acid 20-50 

 parts. When the blocks cut easily, decalcification is complete. (11) 

 Remove the excess of acid by means of powdered chalk. When the 

 chalk no longer dissolves, the acid has been neutralised. (12) Wash in 

 85° alcohol. (13) Section. (14) Treat the sections successively in 90° 

 alcohol and absolute alcohol, clear in origanum oil, and mount in 

 balsam. 



Homy sponges. (3) Absolute alcohol and ether in equal parts 

 (1/2—1 day). (4) Saturate with celloidin (several days). (5) Imbed 

 in celloidin, hardening with chloroform vapour. (6) Cut into blocks 

 and keep in 80° alcohol. (7) Section. (8) Stain with Mayer's picro- 

 magnesia-carmine, picronigrosin, indulin, or Mayer's carmalum. (9) 

 Wash the sections successively in distilled water, 90° alcohol, and 

 absolute alcohol, clear in origanum oil, and mount in balsam. 



Siliceous sponges. (3) Absolute alcohol and ether in equal parts 

 (1/2-1 clay). (4) Saturate with celloidin (several days). (5) Imbed in 

 celloidin, hardening with chloroform vapour. (6) Cut into blocks and 

 preserve in 80° alcohol. (7) Desilicify for one or more days in the 

 following mixture : 90° alcohol 100 parts, hydrofluoric acid 20-40 parts. 

 The vessels in which this stage is carried out must be made of gutta- 

 percha, or if of glass must be coated with paraffiu. (8) When the blocks 

 cut easily, remove the excess of acid by repeated washings in 85° alco- 

 hol renewed frequently during several days. (9) Section. (10) Stain 

 witb Mayer's picro-magnesia carmine, picronigrosin, indulin, or with 

 Mayer's carmalum ; the sections must be kept in 90° alcohol, frequently 

 renewed, before they are stained. (11) Wash successively in distilled 

 water, 90° alcohol, and absolute alcohol, clear in origanum oil, and 

 mount in balsam. 



The procedure of other observers is noticed by the author, but only 

 the remarks relative to impregnation with gold and silver need be quoted 

 here. By means of chloride of gold, nervous formations are easily de- 

 monstrable in many sponges. Impregnation with silver nitrate shows 

 up the limits of the endothelial cells, and the remains of the formative 

 tissue on the sheath of the spicules. In order to effect this impregna- 

 tion, the fragments must be previously immersed in a 5 per cent, solution 

 of nitrate of potash for half an hour to remove the chlorides. It is 

 possible to stain the silver preparations afterwards with picrocarmine. 



Whey-Gelatin with High Melting-point.* — Dr. O. Appel prepares 

 a whey-gelatin which does not melt easily in the following way. 1 litre 

 of separated milk is heated in a water-bath to 40°, some rennet added 

 .and left till it clots. It is again heated, the water-bath being kept on 

 the boil for 1/4 hour, after which it is sieved to separate the whey from 



* Centralbl. Bakt. u. Par., 2 te Abt, v. (1899) pp. 76-2 K 



