SURFACE-SWIMMING FAUNA (INVERTEBRATES). Ill 



its dense opaque body drawn out into five 

 finger -like processes. These features of the 

 animal indicate at once that its life is spent 

 crawling on the sand or rocks at the bottom of 

 the sea. If a Star-fish that has been caught in 

 a lobster pot or brought to the surface attached 

 to the bait on a fishing line, is cast into the sea 

 it sinks to the bottom at once without any 

 apparent effort to swim, to keep afloat, or to 

 arrest its rapid descent. It is therefore clearly 

 unfitted for a surface-swimming existence, but 

 its eggs give rise to larvae which are admirably 

 adapted to it, and can indeed only 

 exist at or near the surface of the 

 sea. These larvae are, as a rule, 

 when first hatched, covered with & 

 number of very minute vibratile 

 cilia, by means of which they swim 

 with considerable rapidity through 

 the water. After a time a number 



- , , , . , , FIG. 31. Young 



of bands appear, which are covered larva of a star- 

 by specially long cilia and then the ^rVchioiaria 

 smaller cilia on the intervals be- stage is 

 tween the bands disappear. 



The precise arrangement of the bands differs 

 in the different species, but from being at first 

 perfectly circular in contour they become more 

 and more curved and twisted, sometimes fusing 

 with one another and in parts degenerating, 

 until, at last, when the larval stage reaches its 

 full development, the bands have assumed an 

 elaborate and somewhat fantastic pattern. 



The body of the larva is, like that of so many 

 surface - swimming creatures, extremely trans- 



