MARINE TELEOSTEAN DEVELOPMENT. 



77 



expansions stretch out from the body in front of them on the 

 yolk. 



2lst April, 7th day. The body is now jerked from side 

 to side by the contraction of the trunk-muscles, and has 

 lengthened ; the caudal extremity is flexed (Figs. 27 and 28). 

 The ear-capsules or otocysts, although they arose in a position 

 behind the head, have now moved forward towards the eyes. 

 The heart forms a long cone with the open end to the left, 

 and debouching into the germinal cavity, while the apex passes 

 to an expansion in the mid-region. 



The heart beats languidly and irregularly, the pulsations 

 sometimes ceasing for 15 or 20 seconds. The gut is hollow as 

 far forward as the heart. The primitive axis, or notochord, is 

 now completely crossed by intermingling arcs. 



FIG. 2!). Egg of Cod with advanced 

 embryo (9th day). 



FIG. 30. Egg of Cod with advanced 

 embryo. 



22nrf April, 8th day. The posterior regions of the trunk and 

 tail are flexed, and the yolk has considerably decreased. The 

 continuous median marginal fin is now in evidence, and the 



FIG. 31. Egg of Cod with more ad- 

 vanced embryo. Lateral view. 



FIG. 32. Egg of Cod with more ad- 

 vanced embryo. 



