36 I. IJIMA : HEXACTINELLIDA. I. 



cut. Practically for the histological purpose the sections need 

 not be thinner than 10 n, since the tissues themselves are every- 

 where exceedingly thin. On the other hand, sections as thick 

 as 50 /i and even up to 100 « or more were found of great use 

 in the elucidation of the general structure. Except for anatomical 

 purposes, an uninterrupted series of sections are of no benefit. 



Sections were fixed on the object-glass by means of the 

 collodion and clove-oil fixative. However, when they were intend- 

 ed to be stained afterwards, the water method was resorted to 

 instead. 



For staining sections on the object-glass, I have come to 

 have a decided preference for the aqueous solution (3?» or 

 stronger) of acid-fuchsin (fuchsin S). It stains quickly and in- 

 tensely, sharply defining the outlines of trabeculse and the beams 

 of the membrana reticularis. I have never gained much by 

 double-staining. This is probably due to the extremely simple 

 state of histological differentiation in the tissues and the consequ- 

 ent lack of parts (except the nuclei) which show any striking 

 difference in the power of selecting stains. It would likely have 

 been a different thing if I had taken into the scope of my in- 

 vestigation the nuclear structure and changes, which I did not. 



