48 Journal of Entomology and Zoology 



8. Ocellus from Linckia colomhiae to show general features. X350. 



Camera lucida. 



9. Ocellus from Aftterina miniata. X350. Camera lucida. General 



view, note the clear central margin of pit. 



10. Tactile organ from terminal tentacle of Linckia colombiae. 



General view showing papillae and details. Camera lucida. 

 X350. 



11. Single sensory cell from Linckia colombiae. Very greatly 



magnified. 



12. Sensory cells from Asterias rtibens showing pigment. Re- 



produced from Cuenot. Osmic acid. Greatly magnified, 



13. General view of eye-pad of Asteropectin erinaceus. X350. 



Camera lucida. 



14. Simple ocellus in an Asterias. Supportive cells dark. Sensory 



cells lighter. Reproduced from Pfeffer. Diagramatic. 



15. A more complex ocellus from Asteropectin rnuUeri. Note the 



lens, other features as above. From Pfeffer. Diagramatic. 



after subsidiance in such a state that they react more readily to 

 stimuli in a distant part of the body than the rosettes near the new 

 stimulus ; 6, There are differences in the characteristics of indi- 

 viduals. 



The opening of the pedicellariae depends upon : 



1. Homogeneous preparatory stimuli 



(a) Sometimes there is no response to the first stimulus. 



(b) Sometimes the first stimulus causes retraction and 

 closing while later ones cause extension and opening. 



(c) Sometimes with large pedicellariae the first stimulus 

 causes momentary opening, the next two or three have no visible 

 effect, the next pronounced opening. 



2. Chemical stimuli of a certain character cause the pedi- 

 cellariae to open later and more readily under mechanical stimuli. 



3. Chemical stimuli of a certain character cause later refusal 

 to open under usual mechanical stimulation, 



4. Holding some object causes the pedicellariae after release 

 to refuse to open under other stimuli. 



5. After closing the pedicellariae often open and close again 

 spontaneously, "snapping." The foregoing action furnishes the 

 condition for the succeeding one. 



In many cases the tube-feet are compelled to do much feeling 

 about before they find the object seized by the pedicellariae. In 

 exploring movements two or three rays are raised from the others 

 and swung about in the water; the other rays creep about. The 

 tip of the arm as well as the other parts of the arm are employed 

 in these feeling motions. 



The relative intensity of illumination on different parts of the 

 body of the starfish may and at times does determine the direction 

 of movement without regard to the direction of the rays of light. 

 The ventral portion of the surface of the starfish is protected by 



