366 J. M. D. OLMSTED 



there is present only a general chemical sense in the starfish and 

 that this is distributed over the whole surface of the body. 



The reactions of holothurians to chemical agents have been 

 studied intensively in only one species, Holothuria surinamensis 

 (Crozier, '14 a), while only scattered observations on the chem- 

 ical sense of synaptids are to be found in the literature. Quat- 

 refages ('42) placed specimens of Synapta inhaerens in solu- 

 tions of opium to quiet them, but was unsuccessful in attaining 

 this end. He also found that fresh water had practically no 

 effect on this species, and that pieces of the animal would re- 

 main alive in it for some eight days. Synaptids were thought 

 by Semon ('87) to have a very keen sense of smell and taste, 

 which he located in the cup-shaped outgrowths on the inner 

 face of the tentacles. These organs had been noted by Quatre- 

 fages ('42, Planche 4, fig. 1 andPlanche 5, fig. 3), who called 

 them 'ventouses.' These are the same structures as Muller's 

 ('50) and Baur's ('64) 'Saugnapfe' and Hamann's ('84) 'Sin- 

 nesknospen.' Semon's reason for locating these special senses 

 in these organs are as follows: (1) pieces of food attached to the 

 ends of the tentacles as they are bent down to the mouth must 

 pass by these cups; (2) histological study of the structure of 

 these organs shows — by far the more weighty evidence in his 

 opinion — that they are lined with cilia and that nerves pass from 

 them to the tentacle nerves. Such ' proof is far from conclusive. 

 Moreover, when Semon makes the statement that bringing a 

 strong-tasting substance, such as chloral hydrate, into the neigh- 

 borhood of the tentacles causes a most vigorous reaction, one real- 

 izes that he is speaking of what we now call a common chemical 

 sense, and nothing so definite as smell and taste. To account 

 for the fact that this ' strong-tasting' substance, chloral hydrate, 

 also stimulated any region of the body to which it was applied, 

 he had to suppose that the 'touch-papillae' contained taste cells, 

 or that such cells were scattered over the surface of the body 

 "to inform the animal as to the good or bad quality of the sand." 

 Clark ('99) found that Synapta rosea and S. inhaerens moved 

 away from rank smelling substances placed in the water near 

 them, even though these substances were not touching the 



