Meduse of the Philippines and of Torres Straits. 165 
Indeed the ultimate size that an individual jellyfish attains before 
becoming mature is a measure of its success in obtaining food, and 
it is interesting to see that the largest jellyfishes are those of the cold 
seas where the floating animal life is more abundant than in the tropics. 
In common with the corals, sea-anemones, aleyonaria, siphonophores, 
and hydromeduse the scyphomeduse are, so far as is known, exclu- 
sively carnivorous and do not feed upon plant life. 
The prey is seized by the mouth, and after being held and partially 
digested in the stomach the remnant is ejected through the mouth. 
The central stomach is a space in the middle of the umbrella, but 
this always gives rise to an outwardly radiating system of pouches or 
tubes which may form a complex network of vessels under the muscular 
layer of the concave side of the umbrella. As this system of pouches 
is connected with the stomach and nutrient fluids derived from the food 
circulate through it, it is often called the gastrovascular system, for 
it is both a sort of ‘‘chymiferous system” and a digestive space. 
In all of the larger jellyfishes, or secyphomeduse, we find within 
the stomach 4 clusters of tentacle-shaped organs of unknown function, 
placed at the broad sides of the cruciform mouth. The smaller jelly- 
fishes, or hydromeduse, lack these stomach-tentacles or gastric cirri 
as they are often called, and in still another structural detail do 
they differ from the scyphomeduse, for the hydromedusze have a 
diaphragm-like membrane which grows inward from the bell-margin 
and partially closes the opening of the umbrella, but the larger jelly- 
fishes (seyphomedusz) do not have a diaphragm of this sort, although 
it is true that the Cubomedusez, or sea-wasps, appear to have such a 
diaphragm, but it is not strictly comparable with that of the hydro- 
meduse. 
The sexual organs of the larger jellyfishes (scyphomeduse) are found 
in the stomach peripheral to, and closely associated with, the four clus- 
ters of gastric cirri. The sexes are usually separate, the animals being 
either male or female, although in rare instances, as in Chrysaora, they 
are hermaphroditic, or male when young and female when old. When 
mature at the breeding season the males and females usually come to 
the surface in great numbers and may congregate in vast swarms many 
square miles in area. The larve or eggs may then be cast out into the 
water by the breaking down of the stomach-wall or the larve may un- 
dergo a part of their development within the stomach, or mouth-parts, 
of the mother, finally to be cast out through the mouth. 
In any event the larve soon develop into minute pear-shaped crea- 
tures about as large as a pin’s head, their bodies being covered with 
vibrating cilia which enable them to spin through the water. For 
a few days or even weeks they may remain thus swimming near the sur- 
face and be drifted far by tide and ocean current. Soon, however, the 
