200 
THE OCEAN WORLD. 
that is, non-sexual or agtmous. These are produced hy bidding, or 
fissiparity, from individuals like themselves. They can also give 
sexual distinctions ; but before this change takes place the creature, 
which was simple, is transformed into a composite animal, and it is 
from its disaggregation that individuals having sexual organs are 
produced, the process being that which has been called alternate gene- 
ration. It goes on in a perfectly regular manner, although it is a fact 
that the young never resemble their mothers, but their grandmothers. 
This great family of Zoophytes Gosse divides into : 
Discophora, having the body in the form of a circular disk, more or 
less convex and umbrella-shaped, moving by alternate contractions 
and expansions of the disk. 
Ctenophora , body cylindrical, moving by means of many parallel 
rims of cilia set in longitudinal lines on the surface. 
Sophonopliora, body irregular, without central digestive cavity like 
the others, having sucking organs, and moving by means of a con- 
tractile cavity, or by air-vessels. 
The Discophora are again subdivided into Gymnophthalmata, 
having the eye-specks uncovered or wanting, a great central digestive 
Fig. 84 . iFciuerea violuceu, natural size (Milne Edwards). 
cavity, circulating vessels proceeding to the margin quite simple or 
branched ; and Steganophiliahnata, having the eye specks protected by 
