32 



Appenduig to Fovrth Annual B^port 



be^-n laid, in about fifteen minutes the egg membrane separates from the 

 yolk, and a clear space apf>ears between the twa A series of cxjmplicated 

 phenomena now take place in the yolk, which results in the separation of 

 format ire and nutritive yolk, and finally in tiie concentration of the 

 former at one pole as the germinal nwund. 



4. Spermatozoa enters the egg in <7r^^ numher^, and not at one point 

 only, but on all &ide^. 



5. The germinal di&c is thus formed under the combined influence of 

 sea- water and sperm. 



Boeck's observations (2) are in harmony with those of Knpffer, except- 

 ing that he states that, trh€t?ier the egg u fertilised or not, a portion of 

 the yolk becomes transformexi into the germinal disc and undergoes a 

 partial segmentation. 



Hoffman (3) combats Kupffer's view tbat the germinal protoplasm is 

 formed under the combined influence of sea-water and sperm, and main- 

 tains that in the herring, as in other teleostean fish, the germinal layer 

 exists before fertilisation. 



Kupffer suggests that the salinity of the water may have some influence 

 on the egg membrane, and tbat possibly it may in certain cases be thus 

 rendered permeable without the previous influence of spermatozoa. 



I have therefore peri'ormed a series of experiments to test the above 

 statements. These were carried on in water which had a specific gravity 

 of 1'24, and at a temperature varying from 41 '8^ F. to 44 •9" F. Kupffer's 

 observations were made at Kiel in water containing only 0'3 — 0*4 per 

 cent of salts ; Boeck, on the other han-i, used water containing 3 per cent, 

 of inorganic salts. 



The following is a list of the more instructive of the experiments which 

 were performed at Eothesay. 



Experimerd 1. — In order to ascertain if the ova and milt retain their 

 vitality a considerable period after the death of the fish, a ntimber of 

 herring were placed in moist cloths immediately after death, so as to pre- 

 vent the eggs from drying up. A number of ova were mixed with milt 

 twelve hours after the death of both fishes, at 3 p.m., 14 '3 85. There 

 was no change in any of the ova at 10-30 a,m. next day, and all were 

 evidently unfertilised. 



Experiment 2. — Eggs were taken from the same female as in experi- 

 ment 1, thirteen hours after death, and mixed with milt frc»m a Ihing male 

 at 4 p.m., 14 3 S5. Within an hour the egg membrane had separated from 

 the yolk in almost all the eggs, and next morning development was going 

 on quite normally. 



Experiment 3. — Eggs were taken at 11 a.m. from a living female and 

 allowed to remain in sea-water an hour before the milt was added, in 

 order to allow the viscous covering of the egg envelope to harden. 

 During this time a few eggs began to develop a hreathing rhamher, but 

 the majority did not alter at all [Kupff"er asserts positively that a 

 breathing chamber is never formed in the egg of the herring until after 

 the penetration of the spermatozoa. Possibly a few living sj^ermatozoa 

 may have been in the water used in this experiment, as it was taken from 

 one of the tanks in the aquarium.] At noon living milt was added, and 

 in half an hour the majority of the eggs were developing a breathing 

 chamber, after which development went on normally. 



Experiment 4. — Ova were taken frcm a fish tbat had been dead forty- 

 eight hours,, and nult added from a Hving male. A separation of the egg 

 membrane from the yolk took place in about 50 per cent, of the esgs 

 some hours afterwards, and in a few the early stages of segmentation were 

 gone through, but somewhat abnormally. 



