14 



INTRODUCTION. 



appearance in as many minutes. The tempera- 

 ture of the water at the spring was 42 ^ Fah- 

 renheit. Since they were brought to the office 

 the water in which they have been kept has 

 varied from 42 ^ to 60 ^ . 



This experiment has afforded us one of the 

 tinest opportunities to be desired for the study 

 of embryolog}^, but profeissional duties have 

 l)revented us from making as minute observa- 

 tion as we could have wished. We have, how- 

 ever, repeatedly and distinctly seen the blood 

 corpuscles in the returning veins enter the 

 auricle of the heart and then pass into the 

 ventricle, and from thence into the aorta. 

 Altogether, it has afforded us one of the most 

 pleasing and instructive lessons in the early 

 stasres of animal existence that we have ever 

 had, and I hope that some person of more 

 accurate powers of observation, and having more 

 leisure, will avail himself of these facilities 

 which are within the reach of every man, and 

 o'ive to the world a more extended statement 

 of facts than I have been able to do. 



Another fact, in which all are interested, has 

 been clearly demonstrated. Any one who may 

 be so fortunate as to possess a spring of water 

 of moderate size can rear this charming fish in 

 o-reat numbers, and the streams that have been 



