ECHIUROIDEA AN ATOMY 



435 



Sehiurus; Thalassema, and the female Hamingia have short pro- 

 boscides, which do not bifurcate but otherwise resemble those 

 of the female Bonellia. 



The green colour of B. viridis is due to a special pig- 



FlG. 221. View of a 

 female Bonellia 

 viridis Rol., opened 

 along the left side, 

 x 2. a, Proboscis 

 cut short ; b, a bristle 

 passed through the 

 mouth into the pha- 

 rynx ; c, convoluted 

 intestine ; d, analtufts 

 or vesicles ; e, ventral 

 nerve- cord ; /, ovary 

 borne on ventral 

 vessel running 

 parallel with e; g, 

 position of anxis ; h, 

 points to position of 

 external opening of 

 nephridium ; i, neph- 

 ridium. This line is 

 on a level with the 

 internal funnel- 

 shaped opening. 



ment, " Bonellein," which at one time was thought to be 

 identical with chlorophyll. A similar green colour is found in 

 Hamingia arctica, Thalassema baronii, and the larvae of many 

 forms. 



A short distance behind the mouth, on the ventral surface, 

 the female Bonellia and both sexes of Thalassema and Echiurus 

 bear two incurved stout chitinous hooks ; these gave the name 



