Euphausiidæ. 39 



Fig. 7. Ovum in a more advanced stage of cleavage. 



» 8-9. Still more advanced stages of cleavage. The con- 

 centric line indicates the inner limit of the ecto- 

 dermal layer, as seen by a dioptrical view of the 

 ovum. 



» 10. Embryo with the first intimation of the 3 pairs 

 of ÎSTauplian limbs, viewed from the dorsal face. 



» 11. Same embryo, viewed from left side. 



» 12. More advanced embryo, with the Nauplian limbs 

 more distinctly defined from the body, but still 

 enveloped by the vitelline membrane; dorsal view. 



» 13. Still more advanced embryo, released from the 

 vitelline membrane; dorsal view. 



Plate 2. 

 (All figures drawn from prepared and stained ova). 



Fig. 1. Still unsegmented ovum, viewed from the lower 

 pole, and with the nuclear area turned to the 

 observer. In the middle the centrosome is seen 

 with its radiating fibres. 



» 2. Another ovum, in which the 1st cleavage is just 

 about to take place. The centrosome has divided 

 into 2 attracting centres, between which the chro- 

 matic substance of the nucleus is received. 



» 3. Ovum, in which the 1st cleavage is finished. In 

 one of the segments a subdivision is about to 

 take place. 



» 4-9. Successive stages of cleavage. In the greater 

 number of cells, the centrosome appears divided 

 into 2 attracting centres connected by a narrow 



