58 University of California Publications in Zoology [VOL. 13 



throughout the block. By this method very little practice is necessary 

 in order to obtain a perfect imbedding. The advantages of such a 

 method are: (1) the certainty that only the desired animals are 

 present; (2) the ease of handling; (3) perfect infiltration; (4) even 

 distribution; (5) the production of a block with a smaller, truer, 

 square cross section than it is possible to obtain by trimming by hand, 

 a point which is very important when good ribbons are necessary. In 

 some respects it is advantageous to stain in toto before sectioning, but 

 the best results are obtained by staining the sections. 



Section Staining. For section staining Mallory's connective tissue 

 stain not only gives excellent results giving four distinct colors but 

 also reveals a very surprising structural differentiation which to my 

 knowledge has not before been described. 



The slides should be run from xylol very gradually down to distilled 

 water. 



Sec. 



Fuchsin S., aqueous solution (%%) 45 



Distilled water 5 



Phospho-molybdic acid (1%) - 60 



Fresh distilled water 5 



Anilin blue, orange G. and oxalic acid 60 



Distilled water 10 



95% alcohol 1 



100% alcohol 1 



Carbo-xylol 1 



Xylol, 

 Mount. 



If the above method is carefully followed preparations may be ob- 

 tained in which the cilia show clear i.e., transparent, the ectoplasm a 

 blue-red, the entoplasm pink, the macronucleus orange-brown and the 

 micronucleus and some fibers which will be described later^how bright 

 red by transmitted light. 



Heidenhain's iron-alum haematoxylin made up as described above 

 for in toto staining also gives very perfect preparations. 



Genus Diplodinium Schuberg 1888 



Schuberg (1888), p. 404. 



Fiorentini (1889), pp. 11-17, pi. 1, figs. 1-4; pi. 2, figs. 1-5; pi. 3, figs. 1-5. 



Eberlein (1895), pp. 251-264, pi. 17, figs. 8-17; pi. 18, figs. 18-20. 



The genus Diplodinium was separated from the genus Entodinium 

 of Stein (1858) by Schuberg (1888). Although Schuberg set up this 

 new genus he gives a very unsatisfactory characterization of it. He 



