72 



WKiHAHD EVANS. 



which is drawn, during- development, into the buccal cavity, 

 while the other is left outside. The position of the intra- 

 buccal half, above the point of union of the salivary glands 

 to form a common duct, tends to prove that it really belongs 

 to the somite of the oral papillge, to which also the salivary 

 glands are related. 



The following tabular form may help to explain the 

 arrangement of the inetameres which constitute the head of 

 Eoperipatus: 



Mesoblastic 

 SomitL's. 



Neivous ganglia 

 or lobes. 



Ventral Organs. ' Appendages. 



I'lie arclii cerebral so- Arcbicerebral lobe 

 mite is vestigial. (dorsal lobe). 



Precephalic 

 processes. 



riie first somite opens Three lateral lobes of 

 to the exterior and the brain, 

 then disappears. 



First ventral organ. Antenna?. 



riie second somite Fourth lobe of the Second ventral organ Jaws. 



disappears without brain ])laced on the' placed above and on 



opening to die ex- dorsal end of the the inner side of 



terior. para-cesophageal the jaws. | 



cords. I j 



riie th.ird somite gives First ventral gan- Third ventral organ Oral papilhe. 



rise to the salivary glion. | divided into two 



gland. ! I halves, one in the 



S I buccal cavity and 



one outside. 1 



From the above table another arrangement of the ventral 

 organs suggests itself, and it must be admitted that there is 

 a good deal to bo said in its favour. The view in question is 

 that the first ventral organ corresponds to the cerebral 

 somite, which has become vestigial ; the second to the first 

 somite ; and that the usimlly described third one should be 

 considered as forming two complete ventral organs and not 

 two halves. On this view one of these would belong to the 

 somite of the jaws and the other to that of the oral papillae. 



