12 



'Jourjial of Comparative Neurology and Psychology. 



ture buds appear in the pharynx, and in the oral cavitV) ^nd on 

 the maxillary barbule, at the same time as nearly as I can deter- 

 mine. Nor does the difference in size between the buds in the 

 three regions which Johnston ('05) finds in Catostomus and Cor- 

 regonus exist in Ameiurus. This was to be expected after it was 

 found, as will be shown later, that buds arise in the oral and 

 pharyngeal cavities simultaneously. 



Series were all cut 7 microns in thickness and all tabulations 

 are based on serial sections, since nothing could be made of the 

 distribution of taste buds from surface views, largely on account 

 of the amount of pigment i.i the epidermis. 



Since the question as to whether a given group is spreading 

 forward or backward from the position in which the buds first 

 appear in a preceding series depends upon the actual length of the 

 specimen compared with the limits of the groups in the two series, 

 a table is given showing the exact age and the age increment, 

 and the average length in all fixing fluids, of the specimens of 

 each age with the average increment in length of each age. 



TABLE II. 



Table showing ages in hours after fertihzation of series K' to U and the average lengths in mm. of 

 these embryos in all fixing fluids and the increments in age and length in each case. 



There are three possible sources of error to be taken into con- 

 sideration in attempting to determine the exact position of a group 

 of buds located on structures that are not segmental and the man- 

 ner of their spreading, (i) All embryos probably do not shrink 

 uniformly. Although a table prepared, but not given in thia 

 paper, shows a rather remarkable uniformity in the various fluids. 



