146 



BIOLOGICAL LECTURES. 



the vegetative pole, or halfway between these poles on the side 

 that zvas 2ipperniost. 



As for the blastodisk itself, tJiat retained its position at the 

 free pole of the egg, near the inicropyie, in ivJiatever position the 

 eggs zuere placed. 



The position of the eggs was plotted in the case of ten eggs 

 attached in the inverted position. 



The coincidence of the first furrow with the embryonic axis 

 was observed in three out of ten cases (Fig. IV). 



The third experiment was made during the summer of '98. 

 A broken bottle from the eel pond was brought into the labora- 

 tory containing a toadfish and a few eggs which had been 

 already deposited by the fish. 



On the morning of July 6 the fish was opened and the 

 mature eggs allowed to flow out of the ovaries and fasten them- 

 selves on pieces of glass. 



About one-third of the eggs set free from the ovaries became 

 fixed to three glass plates. The rest failed to adhere and so 

 were of no use in the experiment. Two minutes was sufficient 

 time to allow for the eggs to become fixed. The plates were 

 then inverted and placed on supports in a large shallow dish 

 with sufficient sea-water to cover them. 



The eggs were then fertilized, and soon after the water was 

 siphoned off by means of a rubber tube and fresh sea-water 



Fig. IV. 



quickly supplied. The dish was so placed that the eggs could 

 be observed from below. 



At 4.30 P.M. — eight hours after fertilization — the first line 

 of cleavage was noted in fourteen eggs, and the direction of the 



