116 



Part III. — Twenty-seventh Annual Report 



was followed in Vc 1 . The former condition was present in the case of Vc. 

 and Vc 2 . 



April 11 and 12. — Vc 2 . — Twenty-seven and sixty-two live fry were 

 obtained on these two days. Some of the fry were smaller than the rest. 

 Some remained curled up in a little ball. They bad possibly been released 

 too early in consequence of the wearing out of the egg -capsule and the agi- 

 tation of the water. Kupffer* said that the egg-shell grew gradually thinner 

 during the development of the egg. The time when hatching takes place is 

 dependent on the amount of resistance that the egg-membrane offers to the 

 muscular action of the embryo. Certain of the larvae had the heads bent 

 down, and they did not swim normally. All the larvae were removed from 

 the box on the 12th. 



April 13, 16, — Six and eight live fry were obtained on these days. 

 On each date the box was completely emptied. Most of the eggs seemed to 

 be hatched ; one live egg was seen. 



April 17. — Vc 2 . — One larva just hatched was obtained. 



April 19 and 20 — No fry was obtained on these dates. Some of the 

 empty egg-capsules were examined. They showed the two-layered structure 

 well. 



The incubation period was from 35 to 42 days. The temperature of the 

 water is shown in Table, p. 118. 



April 2. — Vc. — Some larvae were found in one of the boxes. They did 

 not seem to be quite so large as those hatched from the uncooled eggs. 

 They appeared to have been prematurely hatched. The eyes were not com- 

 pletely pigmented ; the yolk sac was large, and the head was very much 

 flexed. There was no black pigment along the ventral line of the body. 

 The sensory papillae were visible on the side of the larva. It is possible that 

 the zona had given way in consequence of the friction in the box when it 

 was agitated. 



April 12. — Vc. — A quantity of fry was noted on this date for the first 

 time in one of the boxes. 253 were taken out of two boxes. 



April 13, 14. — 100 were removed on the 13th and 800 on the next 

 day. Some eggs were still unhatched ; some were noticed in the process of 

 hatching. 



April 15. — 660 larvae were taken out of various boxes ; 250 at least of 

 them had hatched since the previous day. One box was completely 

 emptied. 



April 16. — 84 live fry were got on this date. 

 1 7 i 



j) 18« 80 ,, ,, 



1 Q AQ 



,, A./. TU ,, ,, ,, ,, ,, 



„ 20. — 57 ,, „ ,, „ „ „ „ There was a quantity of 

 dead fry among the gravel, and also some living fry. 



April 21. — 50 live fry were got on this date. 



99 r> 



9Q K 



Aa. t> ,, „ ,, ,, „ ,, 



>) 6 ,, ,, „ ,, ,, ,, 



„ 25. — Some of the eggs had been shifted on the previous day from 

 the cooled water to water at the ordinary temperature. On this date two 

 larvae were obtained from them, and some of the eggs were still alive. No 

 more fry was got from this lot. No fry was obtained from the cooled 

 lot Vc. on this date. 



April 26. — Vc. — One live larva was obtained. 



* Kupffer — " Ueber Laichen u. Entwicklung des Herings in der westlichen Ostsee." 

 Jahresbericht d. Commission z. WissensclwftU Untersuch. der deutschen Metre in Kiel 

 fur die Jahre 1874, 1875, 1876. Berlin, 1878, p. 32. 



