DESCRIPTIVE CATALOGUE 



OF THE 



PHYSIOLOGICAL SERIES, 



D. 



NERVOUS SYSTEM*. 



INVERTEBRATA. 



Loeb, Comparative Physiology of the Brain, 1901. 



ECHINODEKMATA. 



Cu&iot, Arch, de Biol., t. xi. 1891, p. 445 (Anat.). 

 Romanes & Ewart, Phil. Trans., vol. clxxii. 1881, p. 836 

 (PhysioL). 



IN the Echinodermata there are three distinct systems of central 

 nervous organs superficial oral, deep oral, and apical that 

 occur, either in the form o a circumaxial ring (apical system of 

 Echinids and Ophiurids), radial cords (apical system of Asterids 

 and deep oral system of Holothurians), or more usually as a 

 combination of the two (superficial oral system). All three 

 are not invariably present, and there is also variation in their 

 respective importance. The superficial oral system occurs in 

 all and usually predominates over the others, t>ut in Crinoids it is 

 relatively weak and the chief place is taken by the enormously 

 developed apical system. The apical and deep oral systems are 



* In this volume are included descriptions of the nervous system of 

 Invertebrata and Protochordata and of the brain and spinal cord, with 

 their membranes and blood-vessels, of Vertebrata. 



VOL. II. B 



