16 ILLINOIS BIOLOGICAL MONOGRAPHS [16 



attained the tissues are placed in neutral alcohol and then into 70% 

 alcohol rendered slightly alkaline by the addition of a few drops of an 

 aqueous solution of sodium carbonate. 



Preparations were not flattened but were straightened out on a slide 

 and over this was placed another slide which was supported by strips 

 of paper of such a thickness that little or no pressure was exerted on 

 the specimen by the slides. Dehydration and clearing were accomplished 

 while the preparation was thus kept straight. Xylol and cedarwood oil 

 were used as clearing agents. Preparations were mounted in balsam. 



The methods outlined above yielded very satisfactory preparations 

 for the study of these cestodes and they have also been used by the 

 writer on other cestodes and on trematodes with great success. It is 

 noteworthy that the carmine stains give beautiful preparations of trem- 

 atodes in toto but fail almost entirely for cestodes. For the cestodes 

 these stains fail because they do not sharply and clearly outline the 

 sexual organs as they do in trematodes though not better than do the 

 haematoxylins. In the judgment of the writer the use of the carmine 

 stains on cestode material has been responsible for many errors in the 

 interpretation of cestode structures. 



ANATOMY AND HISTOLOGY OF PROTEOCEPHALIDS 



This section deals in a very general way with the anatomy and 

 histology of the Proteocephalidae, placing emphasis on the usual char- 

 acter of the structures encountered and at times calling attention to 

 variations in this general plan. In the descriptive part of the work the 

 ordinary histological details and many of the anatomical details of lesser 

 importance have been omitted or mentioned in only a casual way. 

 "Whenever the character of a structure has departed from the usual the 

 fact has been noted in more or less detail. 



The cestodes of the family are constructed on a uniform plan which 

 has been thoroly discussed by Monticelli (1891), Kraemer (1892), Rig- 

 genbach (1896), Benedict (1900), Schneider (1905), Schwarz (1908), 

 and La Rue (1909). Some new points are brought out in the present 

 paper. The histological structures of these cestodes have been pretty 

 well worked out prior to the present time. Von Linstow (1891), Monti- 

 celli (1891), Kraemer (1892), and Riggenbach (1896) did pioneer work 

 on the histology of the group. Riggenbach (1896) and Benedict (1900) 

 made very careful and accurate studies of the histology of certain spe- 

 cies of fish Proteocephalids and were able to clear up some of the earlier 

 misconceptions. No careful work on the histology of the amphibian 



