American Fisheries Society. 103 



hatching trough. While no particle of food may be apparent to 

 the naked eye in the bloody water, it is there, nevertheless, and 

 it is carried along with the water at the bottom of the trough, 

 where the fry soon learn to appropriate a part of it as it floats by 

 them. Coral polyps and other marine invertebrates that are not 

 free swimmers depend entirely for their food on the passing cur- 

 rent — food that is not visible to the naked eye, but shown by the 

 microscope to exist in great quantity. 



By this early feeding of fry the nourishment contained in 

 the umbilical sac is augmented, and when the sac is absorbed and 

 the alevin becomes a free-swimming animal, it has become accus- 

 tomed to the liver water, and has acquired a taste for that kind 

 of food. The subsequent surface feeding of liver emulsion then 

 becomes an easy matter. The plan of feeding fry before the 

 absorption of the sac is especially demanded where spring water 

 is used, as it contains no natural food, unless it flows a long dis- 

 tance before entering the hatchery. Where spring water is 

 replaced by stream water as soon as hatching is completed, or 

 where stream water is used entirely, and where, consequently, 

 there exists much natural food in such water, the early feeding 

 of fry is not so imperatively demanded. But if considered in 

 view of the subsequent surface feeding of liver emulsion, which 

 is rendered easier by an early acquired taste for it, as mentioned, 

 it would not be amiss to practice the plan in any case. 



Discrssiox OF DR. henstiall's paper. 



Mr. Clark : I think that it is now generally understood that 

 all trout breeders commence feeding their trout before the sac is 

 absorbed. They go still further than that, and T tliink most of 

 the superintendents and those who are distributing trout, deposit 

 them in the streams before the sac is gone. To deposit trout in a 

 stream Just after the sac is entirely absorbed, is a case of plant- 

 ing fish in streams to die. 



Mr. Titcomb : We formerly planted our fry before the sac is 

 absorbed and before the snow water is out of the stream. We 

 would put them in some times, and I have done so a great many 

 years ago, when our team was carried over the hill on top of four 

 or five feet of snow, on a crust that Avould sustain horses and 

 everything, and then when we got to the stream, we would slide 



