198 



THE OCEAN WORLD. 



that is, non-sexual, or agamous. These are produced by budding, 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 Grosse divides into 

 Discophora, having the body in the form of a circular disk, more or 

 less convex and umbrella-shaped, moving by alternate COD tractions 

 and expansions of the disk. 



Fig. 84. JCquerea violacea, natural size (Milne Edwards). 



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 Gijmnoplithalmata, 

 having the eye-specks uncovered or wanting, a great central digestive 

 cavity, circulating vessels proceeding to the margin quite simple or 

 branched; and Steganoplitlialmata^&vi&g the eye- specks protected by 



