3. 
4, 
5. 
MUSEUM OF COMPARATIVE ZOOLOGY. 99 
The same view of another egg. 
End view of an egg at the stage of the primitive cumulus. 
View upon the anterior end of the egg from which Fig. 2 was drawn. 
The larger polygons are boundaries of yolk masses, the smaller those 
of blastoderm cells. 
PLATE II. 
6-11 are side vews of eggs, and are arranged in the order of their sequence 
i0. 
11. 
ig. 12. 
in development. 
Left side of the embryo at the stage which exhibits six protozonites. 
View of the right side at the stage marked by the beginning of the 
appendages. 
A more advanced embryo (left side) with incurved permanent appendages 
and four pairs of provisional appendages. 
A somewhat oblique view of the right side during the period of reversion, 
showing the rudimentary terga (trg.), also an increase in the distance 
between the cephalic and caudal lobes. 
Embryo (left side) when reversion is nearly completed, showing the per- 
sistence of the two posterior pairs of provisional appendages, and 
also their change in position to the posterior part of the body. 
Embryo after the reversion is completed ; the last two pairs of provisional 
appendages are being modified to form the spinning mammille. 
PLATE III. 
The head and tail lobes at the stage when the appendages begin to 
appear. 
13-17 form a series of dorsal views during reversion. 
13. 
14. 
15. 
16. 
17. 
18. 
19. 
20. 
Dorsal view of an embryo at the beginning of reversion. 
An embryo a little further advanced, to show the separation of the head- 
and the tail-lobes, and also the increase in the dorsal extension of the 
tergites. 
A similar view of an embryo a few hours older than the preceding. 
Dorsal aspect of a still older embryo, in which the tail-lobe is just disap- 
pearing from the dorsal surface. 
An embryo at about the stage represented in Fig. 11. 
PLATE IV. 
. 18-28 present a series of ventral aspects. 
An embryo at the stage which shows six protozonites. 
An embryo showing the beginning of the appendages; it is of the same 
age as that shown in Fig. 7. 
View of the caudal lobe at about the same stage as is represented in 
Fig. 8. 
Ventral view during the period of reversion. The embryo corresponds 
nearly with the stage represented in Figs. 10 and 16. 
Ventral aspect of the embryo from which Fig. 14 was drawn. 
