ELEVENTH ANNUAL MEETING. 9 
lows. I have believed heretofore that every portion of the sac 
was necessary to the complete development of the fish; and have 
been rather amused at the innocent question given above. All 
fish-culturists have noted the fact that an embryo with a small 
coagulation in its sac, caused by an injury while.in the egg, or 
after hatching, will die near the time that the injured portion is 
about to be taken up by the absorbent vessels; but, to my sur- 
prise, I have seen portions of the sac thrown off this winter, and 
the fish have lived and taken food afterward. 
In the hatchery of Mr. Thomas Clapham, at Roslyn, L. L, 
which I fitted up the past winter to hatch salmon for Prof. Baird 
and Mr. Blackford, the troughs were all new, and the haste with 
which they were made allowed but little time for coating with 
tar. One trough in particular had but a very light coating, and 
soon after the hatching of the eggs a singular spotted appear- 
ance was observable among the fry. This was caused by the 
turning white of their livers. Both Prof. Ryder and myself ex- 
amined them under the microscope, and saw the clouded liver, 
through which the blood appeared to circulate feebly. Know- 
ing no other cause than the exudations of unseasoned pine 
wood, I removed the fry at once, and placed them in a well 
tarred trough, and watched the result. Neither Prof. Ryder nor 
myself thought that the fish, some 15,000 in number, could live. 
He was of the opinion that the trouble originated in the sac, 
and that a deficient circulation in some portion had affected the 
liver. It was a new experience to both of us, and his extensive 
knowledge of embryology gave his opinion a weight which led 
me to accept his view, although I could not see any trouble in 
the sac at this time. I gave him some specimens afterwards 
which confirmed this theory, which I am now satisfied was a 
correct one. 
The first indication of trouble in the sac was an elongation of 
the posterior portion of it, and a constriction about midway 
between its extremity and its connection with the body. This is 
shown in the specimens here before you in the vials Nos. 1 and 
2. Sometimes the portion beyond the constriction contained 
the large oil globule, and sometimes it did not; and this globule 
seemed to be very irregular in its position. All the fish in the 
