ECHINODERMATA (THE STARFISH) 

 MORPHOPHYSIOLOGIC STUDY 



A. External Morphology 



1. General Shape? Use of this shape to the starfish? 



2. Symmetry. 



(1) Radial or bilateral? 



(2) Advantage of this? 



3. Arms or Rays. 



(1) Number in your specimen? 

 ■ (2) Size? 



4. Aboral Surface. The surface upon which the mouth is 

 situated is called the oral surface, and the surface opposite the 

 mouth, the aboral surface. 



(1) Shape of the aboral or upper surface? Use? 



(2) Aboral Spines or Projections. 



(a) Shape? 



(b) Number? 



(c) Use? 



(3) Madreporic Plate. Look between the bases of two of 



the rays for a wart-like or sieve-like plate. 



(a) Color? 



(b) Use? 



(c) Into what do its perforations lead? 



(4) Pedicellarise or pinchers. These are soft, flexible 



projections among the spines. Scrape off a httle of 

 the spiny mass. Mount it in water on a sUde, and 

 examine under the microscope (X 100). 



(a) Estimate the number on one ray. 



(b) Position? 



(c) Structure? 



(d) Use? 



(5) Sketch the aboral surface (1), naming all parts studied. 



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