274 BULLETIN OF THE 



PLATE 11. 



Fig. 1. Four-cell stage, two hours after PI. I. fig. 13. 

 " 2, The same, two hours and five minutes after. 

 " 3. Segmented ovum sliowing the beginning of the tertiary furrow (3 cl. pL), 



two hours and fifteen minutes older than that represented in PI. L 



fig. 13. 

 " 4. Four-cell stage, two hours and twenty minutes older. 

 " 5. The same, two liours and twenty-five minutes older. 

 " 6. Older stage, two hours and thirty minutes after Fig. 13. .50 mm. in 



diameter. 

 '* 7. Segmented ovum, two hours and forty minutes older than Fig. 13. 

 " 8. Superficial granular layer (ctoi.) formed on the segmented ovum. Planula ? 



.45 mm. in diameter. 



PLATE in. 



Segmented egg with a marked increase of thickness of superficial layer at 



dm. .54 mm. in diametei'. 

 The same, treated with acetic acid (two layers at pole, ch., lih.). 

 An older egg, in wliich the thickness* of the two layers is more marked. 



.60 mm. in greatest diameter. 

 The same, older. 



The same, still older, showing the cavity of the primitive larva (c. ^). ?.). 

 A portion of the egg and the growing protuberance at its pole. 

 The same, older. 



8, An older larva, with constriction between the scale and the surface of the 



ovum. 



9. The same, ol<lor. The right side of this figure corresponds with the left 



of preceding and following figures, except in Fig. 12. 



10. Embryo of about the same age as the last, reversed. 



11. Embryo found in water, August 8 (adult put in August C), a little older 



than the last. 



12. Embryo still older. 



13. The same, older, .47 mm. in diameter. 



14. A primitive larva taken on the third day after the capture of the adult 



(72 hours old l), .70 mm. in diameter. 



15. A larva a little older than the last, seen from the pole opposite that on 



which the primitive hydrophyllium is formed. The larval appendages 

 are therefore for the most part seen through the yolk. 



16. A larva so placed that the axis of tlie future Agahna is almost vertical. 



Tlie union of the primitive hydrophyllium and the yolk is on the side 

 of the yolk turned away from the observer. Older than last. 



