384 I' n i versify of California Publications in Zoology. [VOL. 6 



uneven to be of special value. Mayer's acid haemalum, Dela- 

 field's haematoxylin and Ehrlich's haematoxylin gave satisfac- 

 tory results for general morphology. Lonnberg's borax carmine- 

 Lyon's blue method gave the best result for the study of the 

 nervous system. This in general is the method used by Lonn- 

 berg in his work on Gyrocotyle. A brief description of the 

 process is given by him (Lonnberg, 1891). The material is 

 stained in toto in Grenadier's alcoholic borax carmine, 60% 

 alcohol, decolorized in acid alcohol (5 drops cone. HC1 to lOO 

 cc.) ; after sectioning and mounting the sections are run very 

 quickly through absolute and 90% alcohol to a saturated solution 

 of Lyon's blue in 60% alcohol, plus three drops n/10 HC1 to 

 35 cc. of stain, where they remain fifteen minutes. The sections 

 are decolorized in ammoniacal 85% alcohol made up of one part 

 85% just basic to litmus to 4 parts neutral 85%. Decolorization 

 requires from two to three minutes and must be stopped when 

 the sections appear violet in color. On washing in neutral 90% 

 the differentiation takes place. The sections must not be left 

 in 90% or absolute longer than one or two seconds, else -the stain 

 is blurred. This method gives beautiful preparations in so far 

 as differentiation of tissues is concerned, but is rather poor for 

 cytological differentiation, especially in cell-boundaries. 



The nervous system stains uniformly a light blue, easily dis- 

 tinguished from all other tissues except condensed connective 

 tissue. The blue is clearer in the nerves than in the connective 

 tissue; the nervous tissue can easily be recognized with a fair 

 degree of certainty by this fact, coupled with its distinctive 

 histological structure. 



The statement generally made that Lyon's blue should be 

 used in very dilute solution for corrosive sublimate material is 

 not applicable in this case. Weak solutions give no result, for 

 all the color drops out at once, leaving no differentiation. 



II. BODY-COVERING AND SPINES. 



The body is covered by a thin membrane, composed of finely 

 felted fibres imbedded in a homogeneous matrix (cut., pi. 42, figs. 

 55, 58). These fibres are exceedingly delicate, tangled in an 

 irregular fashion, but in general parallel to the surface of the 



