Fic. 
6. 
[os] 
PLATE XII. 
Portion of the disk of a young Porpita, measuring over ;},” in diameter, seen from the upper side. 
Same seen from the lower side. 
Portion of the disk of a young Porpita, measuring 3,” in diameter. 
Young Porpita, measuring ;%;” in diameter, in which a portion of the disk of the vascular system 
has remained simple. Seen from above. 
Portion of the disk of a young Porpita, nearly in stage of Fig. 4, seen from above, but the vascu- 
lar system is branching. 
Portion of the disk of a young Porpita at about the same stage with simple vascular system, but 
proportionally longer tubes. 
Portion of the disk of a young Porpita about in stage of Fig. 6, seen from the lower side of the 
disk, 
Portion of the disk of a young Porpita somewhat more advanced, the vascular system more 
branching. 
Fics. 9, 9. Portion of the disk of a young Porpita measuring about }” in diameter. The ramifications 
Fig 
Fie 
Fie. 
Fic 
Fic. 
Fig. 
- 10. 
Su tits 
12. 
. 13. 
14. 
15. 
of the vascular system are limited to the margin of the mantle. 
Portion of the disk of a young Porpita measuring ;8,” in diameter. 
Portion of the disk of a Porpita measuring not quite }/’ in diameter. 
Marginal folds of the edge of the mantle. 
Portion of the disk of a Porpita measuring 1” in diameter, showing the system of anastomos- 
ing tubes of the mantle. 
A portion of the same, showing the star-like irregular termination of this anastomosing system. 
Magnified view of a part of the white plate. : 
