44 



FIRST LESSONS IN ZOOLOGT. 



to absorb; finally, the larval body disappears. At this time 

 the starfish is still minute, conical, disk-shaped, with a 

 crenulated edge. In this condition it remains probably 

 two or three years before the arms length- 

 en and it becomes of full size. 



FIG. 43. Asterias vulgaris. (Natural size.) 



es 



FIG. 43. Brachiolariaof 

 Asterias vulgaris, en- 

 larged, with the star- 

 fish ()) developing at 

 the aboral end; e, me- 

 dian anal arm; e 6 , odd 

 terminal oral arm; /, 

 bracln'olar arm; f 1 , 

 branch of water- tube 

 (low') leading into /", 

 odd brachiolar arm. 



The changes or transformations of the starfish as well as 

 other Echinoderms are intimately connected with the pres- 

 ervation of the species. Full-grown starfish are heavy, 

 slow, inert creatures, and do not move far away from their 

 homes among oysters, mussels, and under stones or sea- 

 weed; but in their infant or larval stages they are, as we 

 have seen, entirely different creatures, swimming as trans- 

 parent, animated bits of pinkish jelly at the top of the 

 water, and borne about in vast numbers by the ocean cur- 

 rents hundreds of miles from their birthplace. Perhaps 

 they would be snapped up by fishes and other animals were 

 their bodies not so transparent; as it is, were all the adult 



