i8o Journal of Comparative Neurology. 



excellent and have given me the preparations upon which 

 most of the work has been done. These experiments I 

 have fully reported upon in a previous paper ('98), and I 

 give here simply the one method which was employed in 

 the preparation of the series upon which the plots and 

 most of the descriptions and other figures are based. The 

 general appearance of these sections is well shown by 

 Figures i and 2, drawn for me by Mr. Veenfliet. 



After fixation for two or three weeks in Flemming's 

 stronger fluid, frequently renewed, and paraffin embed- 

 ding, serial sections were cut 15 micra in thickness. 

 Medium-sized adults were chosen, the head severed from 

 the body behind the pectoral fins and mounted entire. 

 To ensure the proper permeation of the paraiHn it is well 

 during the embedding to aspirate the specimen under the 

 air pump or with a syringe and thus remove from the 

 cavities of the body the gases evolved in the decalcification. 



The sections may be fixed to the slides with Mayer's 

 albumen, first floating them out on warm water, if 

 necessary, to remove all wrinkles. After passing them 

 out of the absolute alcohol one may flow over them a very 

 thin solution of celloidin. Drain quickly, and allow to 

 set before passing down into the lower grades of alcohol. 

 In this way is averted the danger of the sections becoming 

 loosened in the subsequent manipulations. From water 

 the sections pass into a mordant composed of saturated 

 solution of copper acetate, two volumes; water one 

 volume. Here they remain six hours or longer at ordinary 

 summer temperature, after which they are thoroughly 

 rinsed in water and then treated with Weigert's haema- 

 toxylin for four hours or longer. Decolorize in Weigert's 

 decolorizer, wash thoroughly (one hour or longer, in run- 

 ning water) and mount in the usual manner. 



