CHAPTER XVI. 

 BALANOGLOSSUS. 



Class Hemichordata. 



This class has been established for the reception of the 

 worm-like Balanoglossus, which has at least some remarkable 

 approximations to Vertebrate structure. Along with it, 

 Cephalodiscus should probably be ranked, and possibly the 

 genus Rhabdopleura as well. It is possible that morpholog- 

 ists have made too much of the resemblances between these 

 forms and Vertebrates, and too little of the differences, but 

 the acceptance of the class Hemichordata may serve at leafet 

 as an illustration of the absence of hard and fast lines in 

 classification. 



The Genus Balanoglossus. 



The species which form this genus are worm-like marine 

 animals, occurring in the English Channel, the Mediterranean, 

 Chesapeake Bay, etc. They live in sand or mud, and 

 exude mucus. In length, they vary from about an inch to over 

 six inches, their colours are bright, their odours peculiar. 

 They are very readily broken — in capture at any rate. The 

 sexes are distinct, and the colours of the males are slightly 

 different from those of the females. A species of Balano- 

 glossus was described about the end of the i8th century by 

 Delle Chiaje ; Kowalevsky, who did so much to elucidate the 

 nature of Ascidians and Amphioxus,, also described this type ; 

 but it is only within the last few years that the researches of 

 Bateson and others have led zoologists to appreciate its 

 importance. 



