THE AMPHIOXUS. 



addition of the peculiar gland of the Amphioxus larva. 

 At the end of this period, however, takes place the 

 perforation of the mouth and first gill-slit. Some 

 hours later the anus also appears. 



The following table will give more exact informa- 

 tion with regard to the times of development p.nd 

 their variability : 



FIEST DAY. 



FIRST SERIES. 



SECOND SERIES. 



THIRD SERIES. 



o CLOCK 



8.30. Stage, Fig. 

 29. 



9.30. Stage, Fig-. 

 31. 



10.15. Embryos be- 

 gin to ro- 

 tate. 



O CLOCK 



8.15. Stage, Fig. 

 20.' 



9.0. Stage, Fig. 

 29. 



9.45. Stage, Fig. 

 31 (begin 

 to rotate). 



10.30. Stage, Fig. 

 33.' 



ll.CO. Stage, Fig. 

 33.' 



11.15. Stage, Fig. 

 35. 



O CLOCK. 



8.30. Stage, Figs. 

 31-33. 



9.0. Stage, Fig. 

 33. 



9.45. Stage, Fig. 

 35. 



10.30. First Meso- 

 blastic So- 

 mite. 



11.0. 2 Mesoblastic 



Somites. 



11.30. 2-3 Meso- 

 blastic So- 

 mites. 



