700 JOSEPH MANGAN. 
the bulk of the foreign cells in the canals and tissues of the 
colony may come from the surrounding water at a subsequent 
period. An apparent increase in the substance of a mature 
ovum (see below) might be an indication of their activity. 
At all events, there is suggested, an approach to a more com- 
plete symbiotic union than that which exists in Convoluta 
roscoffensis, for instance, where it has been definitely 
shown (’07) that infection takes place after the animal is 
hatched, for there the animal undoubtedly plays, in the long 
run, the part of a parasite with respect to the alga, as under 
no known conditions were algz found to escape alive from 
the body of that turbellarian. 
THe Menus. 
Male meduse of Millepora have up to the present been 
found only in material from Torres Straits and from Funa- 
futi (91), and none of these had been extruded from the 
colony, though some lay free in the ampulle. However, 
along with the liberated female meduse from Jamaica were 
two free male medusew, one of which is figured (fig. 17). 
The most noteworthy feature of the anatomy at this stage is 
that the margins of the umbrella are furnished with some 
batteries of nematocysts. They are the largest of the smaller 
of the two varieties of stinging cells peculiar to Millepora. 
The manubrium is practically devoid of zooxanthelle. 
The anatomy of the female medusa has been figured and 
described by Hickson (’99), and is exhibited to some extent 
in figs. 8 and 9. In the later stages of the meduse, within 
the ampulle, the substance of the umbrella becomes thinned 
out centrally into an excessively fine membrane (fig. 9). 
The structure of the liberated female medusa was exhibited 
fairly well in afew cases. A portion of a medusa, shortly 
after liberation, is shown in transverse section (fig. 10). A 
stage is also figured in which the eggs are evidently com- 
pletely developed and ready for liberation (fig. 12), and, at 
