300 



ANNELIDA. 



fact, as well as the formation of the prseoral lobe and the develop- 

 ment of the ventral hooked setae, points to a close relationship with 

 the Chcetopoda. In the adult animal, however, the internal segmen- 

 tation is very little marked. The dissepiments, with the exception 

 of the first, which forms a partition between the head and the body, 

 are lost, and the segmentation of the ventral cord is only indicated 

 by the distribution of the nerves. The supra-cesophageal ganglion 

 remains at the apical region of the praeoral lobe (proboscis) ; hence 

 the 03sophageal commissures are extraordinarily long. 



The strongly developed praeoral lobe forms a proboscis -like 



FIG. 314. a, female of Bonfllia vlridis (after Lacaze-Duthiers). I, Integument and generative 

 organs after the intestine has been removed. Hd, Cutaneous glands ; Ab, anal vesicle ; 

 Ad, rectum ; Or, ovary ; Tr, ciliated funnel of the uterus (f). c, Anatomy of Bondlia 

 viridis (after Lacaze-Duthiers) . D, alimentary canal with anal vesicles (Ab) ; M, mesen- 

 tery ; U, uterus ; JK, proboscis. 



appendage which may develop to a considerable length and become 

 forked (Bonellia) (fig. 314 a). 



A pair of hooked setae (with reserve setse in the sheath of each 

 seta) are always present on the first segment of the body. In 

 Ecliiurus there are also one or two circles of setse at the posterior 

 end of the body. There are from one to three pairs of anterior 

 segmental organs (so-called brown tubes or ventral glands), which 

 open on the ventral surface and are used for the passage outwards 

 of the generative products. Besides these there is also a pair of 



