3IILNER FISHERIES OF THE GREAT LAKES. 55 



of the under fins tinged with blue, and the abdomen swollen at this 

 period. 



(22 /.) JDevelojmient of eggs and embryo. — It has been proven by repeated 

 observation by fish-culturists that the higher the temperature of the water 

 in which the eggs are placed the more rapidly the embryo fish develops 

 within the egg, and the sooner it escapes from its inclosure in the shell. 



The temperature of the succeeding months after the spawning-period 

 probably regulates to a considerable extent the time of hatching of the 

 white-fish in the lakes. 



On the 11th daj'^ of April, at Ecorse, on the Detroit Eiver, I visited 

 Grassy Island in companj" with Mr. George Clark. The inside of the 

 bag of a seine was lined with millinet and dragged in the river, bringing 

 ashore a great quantity of mud and the small forms of life inhabiting 

 the bottom. Sifting and washing out tbe mud resulted in finding one 

 little worm-like fish-embryo, one-half inch in length, which I at once 

 suspected to be the specimen sought after. Other attemx)ts with the 

 seine failed entirely from taking any more. 



Mr, Clark then proposed that we take a boat and search carefully on 

 the surface for the young fish. Taking a pail and dipper, we shoved off 

 our boat, and Mr. Clark pulling very slowlj" with the oars, I hung over 

 the gunwale, and in a very few minutes found a little, active fish swim- 

 iug with his head at the surface, and captured him with the dipper. He 

 X)roved to be identical with the one taken with the seine. In the course 

 of half an hour we captured forty, all of the same size and state of de- 

 velopment. Most of them were taken within five or six inches of the 

 surface, though they were frequently seen coming up from as far below 

 as they were visible. They were nearly white, with, a pair of large black 

 eyes, were very active, moving continually, propelling themselves with, 

 a constant motion of the tail, and swimming with the head up and the 

 body depending at an inclination of about fifty degrees. They seemed 

 apprehensive of danger, and turned quickly from the dipx)er when it 

 came near them, occasionally escaping. They had no gregarious instinct 

 whatever, and thougli occasionally taken in j)airs it was probably an 

 accidental circums'tauce. 



On April 14 we again visited the island and caught a number more of 

 the young fish. 



A few days later Mr. Clark and I visited the breeding-house of Mr. 

 X.W. Clark, of Clarkston. He had put down a large quantity of white- 

 fish ova in November, and had taken the water flowing over the eggs 

 from a pond that had remained frozen over nearly all the winter. The 

 temperature of the water had remained at 34° or 35°, and the young 

 fish had begun to hatch out on the 1st of April, and about the 9th or 

 10th were all out of the shell. This temperature is probably much 

 the same as Detroit River at Ecorse, sixty-eight miles below Lake 

 Huron, the current flowing at the rate of two miles per hour. 



The appearance of the umbilical sac in the specimens from both 



