THE MALAYAN SPECIES OF ONYCHOPHORA. 71 



seem to correspond to the cephalic processes discovered by 

 von Kennel, and interpreted as the primitive cephalic antennae. 

 The lateral lobes of the brain, collectively, correspond to the 

 first somite, and there seems to be no reason whatever for 

 regarding- them as separate ganglia representing metameres 

 which have disappeared. They are situated in front of the 

 ganglion which supplies the jaws, and which does not, 

 properly speaking, form a part of the brain. The connec- 

 tion between the ganglia of the jaws and the brain is a 

 ventral one (PI. 9, figs. 22 h and 22 c., lo^), similar to that 

 occurring between any two pairs of ventral swellings of the 

 nerve-cords. The nerves to the jaws are given off from 

 points situated near the dorsal ends of the fourth lobes, 

 one of which is shown on the left side in fig. 22 c, just 

 below the line marked lo.^. As far as the structure of the 

 brain can be relied upon, it gives no indication of any meta- 

 meres having disappeared. The dorsal lobes seem to repre- 

 sent the archicerebriim ; the three lateral ones are merely 

 differentiations in the portions corresponding to the first 

 somite, while the fourth lobe supplies the jaws, and conse- 

 quently belongs to the region of the second somite. 



The ventral organs arise in a manner which has been fully 

 described by von Kennel and by Sedgwick, and there is no 

 object in further describing them here ; but it seems neces- 

 sary to discuss their relation to the nervous ganglia and the 

 mesoblastic somites. It would seem that the anterior one 

 corresponds to the first pair of somites and to the three-lobed 

 brain, and not to the cerebral somite and archicerebrum. 

 The second pair of ventral organs belong to the metamere 

 which carries the jaws, above which they are immediately 

 situated, though they have acquired a secondary relation to 

 the second and third lobes of the brain (PI. 9, fig. 23 fc, 

 V. 0.^). Their relation to the jaws seems more important than 

 to the brain, for the latter seems to have been brought about 

 by the secondary shifting of the mouth parts. On this view 

 of the second pair, the third pair of ventral organs must be 

 considered as having been divided into two halves, one of 



