470 . THE AMERICAN NATURALIST. | [Vor. XXXVI. 
(Linn.) and Favia fragum (Esper). A colony of Manicina will 
sometimes possess five or six adhering young polyps, the dif- 
ferent members of which exhibit one, two, three or more oral 
apertures, and in other ways are regularly developed. Their 
structural details prove that they have originated not by fission 
or budding, but from larvze which have settled, probably imme- 
diately or shortly after extrusion, in close association with the 
parent colony. Colonies of Manicina and Favia are often 
found charged with larve, and their extrusion has been fre- 
quently observed. 
Much variation exists as to the activity displayed by the 
larvae of these and other coral species immediately on extru- 
sion. In some cases the larva are quite vigorous, and able to 
swim about from the beginning; and under natural conditions 
these would no doubt continue their activities for a long time, 
and might be drifted great distances before settling. Others 
again sink immediately on liberation from the interior of the 
parent, and falling upon the nearest object may settle there. 
In most instances the nearest object will be the dead lower 
part of the parent colony. It is thus easy to see how, under 
ordinary natural conditions, such aggregations as those found 
by von Koch and Lacaze-Duthiers may have arisen. The 
grouping of the larva in S. radians appeared to be less fortui- 
tous than this, for practically all the specimens were able to 
swim about immediately on being set free. It may be that 
the tendency towards aggregation above described was in some 
way influenced by the cramped artificial conditions of the small 
aquaria. ; 
The possibility of extruded larve settling in numbers imme- 
diately around the parent, instead of drifting widely apart, is a 
phenomenon likewise to be looked for in the field study of the 
closely allied Actiniaria. On the coral reefs in West Indian 
waters occur large irregular patches, often several feet across, 
of one or other of the anemones, Actinotryx sancti- Thome 
Duch. & Mich. and Ricordea florida Duch. & Mich. The 
polyps are usually adherent to some dead coral slab, and in 
a single patch there may be hundreds of individuals. Both 
species exhibit asexual reproduction by fission, and in any 

