142 FISH HATCHING. 



myself for some time past, and by the in- 

 valuable aid of the microscope have, I think, 

 succeeded in unravelling the mystery. After 

 a most careful examination of the living and 

 the dead fish I came to the conclusion that 

 the duct was not there. I found, however, 

 a mark which, cursorily examined, might lead 

 a person to suppose that some duct existed, 

 but across which the circulation was proceed- 

 ing vigorously ; but of the supposed bifurcated 



termination of the duct there was no sign 

 whatever. Having discovered what was not, 



it remained for me to discover what was : I 

 have now to report the result of my inves- 

 tigation. 



The umbilical vesicle consists of a double 

 sac containing fatty matter. The inner of 

 the two sacs is covered with a network of 



