Notes on Sense Organs in Some Asteroids 



ARIHUR S. CAMPBEl.l, 



The sense organs of many species of starfish have been well studied during the 

 past fifty years by a number of competent observers. Among the earlier important 

 studies are those of Haeckel, 186U; Wilson, 1862, and Hamann, 1885. Later work, 

 especially the more minute observations are the subjects of study of Ciienot, 1887, 

 and of Pfeffer, 1901. 



Materials for this study include most of the common littoral asteroids occurring 

 at Laguna Beach. Representatives of six species, the members of three orders, were 

 examined. All preparations were fixed in HgCI.- and double stained, first in hema- 

 toxylin and then in picro-fuchsin. 



Eyes are placed at the terminus of each ray, and just proximal and ventral to 

 the terminal tentacle. In nearly all species they are well protected by a strong 

 circlet of heavy spines. They are mostly of a deep red color whicli is slowly 

 soluble in alcohol. 



Viewed more closely the eye-spot appears as a pad in which there are a number 

 of little depressions; these are the ocelli. Each presents a separate structure, the 

 whole eye-spot being mereK' a composite of many ocelli. 'I'he number of ocelli 

 varies greatly. 



The histology of the ocelli in these forms has been disputed by several observers. 

 Most of the earlier workers believed that lenses are present. C'uenot, 1887, does not 

 accept this, but Pfeffer, 1901, indicates a lense in .-Isteropertiri miilleri. In some of 

 my preparations there is a little indication of an epithelial thickening bridging the 

 eye-cavity, but mostly the eyes show a clear and rather wide, open space freely in 

 communication with the exterior. These preparations Indicate somewhat an inter- 

 mediate condition between the two figures reproduced from Pfeffer. 



Cells forming the eye are of two types. The several reproduced from Cuenot's 

 paper, fig. 12, are pigment cells or sensory cells of the retina. They are surrounded 

 and supported b\' cells of a second type; the so-called supportive cells of Cuenot 

 and others. 



The comparati\'c structure of several eye preparations is figured. The suji- 

 portive cells are well stained with fuchsin. 



A sense organ in starfish was seen in l.iinkia lolnmhhe Grey, among my prepara- 

 tions in the course of this investigation. It is probahlv a tactile organ. It is seen 

 in the ventral portion of the terminal tentacle, near the eye-spot. It consists of a 

 nutnber of papilla extending over a restricted area of the tentacle. The papillae are 

 pronounced and have a similar structure to those found in other forms. They 

 follow through a small series of sections rather completely, showing constant form. 

 These may be like the so-called organs of taste described by Eimer, 1880. 



(('.iinlriliuliiiii from llir '/.onlogicnl I.iihnratnry nf Pnmiinn ('iillcye) 



KIBUOCJRAPHY 

 CUKNOT, L. 1887. 



Contribution a I'etude anatomique des Asterides. 



Arch, de Zool, Kxp. ct Gen., 2c serie, vol. 5 /'/.( (supp.) p. 52-pl. 3, fig. 11-18. 

 ElMER, Th. 1880. 



