PROTOZOA. 377 



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 528). 



Impregnation with Silver (see 202). 



Larvae of Spongiae. SCHULTZE (Zeit.f. iviss. Zool.j xxxi, p. 295) 

 places the ova and larvae of Sycandra raphanus in hanging- 

 drop moist chambers, oxygenated by means of a few fronds 

 of green algae. He also (ibid., xxxiv, 1880, p. 416) found that 

 the best sections of the more advanced sessile larvae of Plakina 

 were obtained by selecting larvae that had settled down on 

 thin fronds of algae and treating them, together with the 

 fronds, with osmic acid, then alcohol of 52 per cent., alum- 

 carmine, Aq. dest., alcohol of 52 per cent., then 70 per cent., 

 95 per cent., then absolute alcohol, turpentine, and finally 

 paraffin. 



Protozoa. 



750. Introductory. Since the Protozoa may be considered 

 as free cells, and their peculiar organs known as " nucleus " 

 and " nucleolus," " macronucleus " and " micronucleus," &c., 

 present in the main the same reactions as cell-nuclei, it is 

 evident that the reagents and methods of cytology are in great 

 part applicable to this group. .One of the most generally 

 useful of these reagents will be found in the acid solution of 

 Methyl green; it is the reagent that allows of the readiest and 

 best demonstration of the presence and form of the nucleus 

 and nucleolus (BALBIANI et HENNEGUY, Compt. rend. Soc. de 

 Biol, 1881, p. 131). 



Amongst useful reagents not mentioned in the following 

 descriptions of the methods employed by different authors, I 

 call attention to the weak solutions of alum, potash, and borax, 

 which serve to demonstrate the striations of the cuticle and 

 the insertions of the cilia of Infusoria. 



751. Staining intra vitam. The possibility of staining Infu- 

 soria infra vitam was discovered independently and almost 



