56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I37 



Unfortunately Pflugf elder does not figure them in whole mounts in 

 his paper, but Sedgwick (1885) for Peripatits capensis, and Kennel 

 (1884, 1888) for Peripatus edwardsi and Peripatus torquatus, show 

 the arrangement of the ventral organs very clearly from the ventral 

 side. Figure 5 A of Peripatus capensis illustrates an early stage in 

 the development of the ventral side of the embryo. In this figure, 

 though the lips of the oral cavity are already forming, the appendages 

 of the second visible segment which will become the feeding claws 

 are still located laterally. Adjacent to them the lobes that will form 

 the feeding claws are evident, and the relationship of the future 

 feeding claws to this segment is unmistakable. In figure 5 B the lips 

 have become much more extensive and the feeding claws have begim 

 to withdraw into the preoral cavity and with them the ventral lobes of 

 the second segment. The antennae and the antennal lobes are distinc- 

 tive from the first, and the appendages of the segment following that 

 of the feeding claws show by the presence of the forming orifice that 

 they will become the slime glands. Figure 5 C shows the ventral organs 

 lying adjacent to each other along the center line. The segments indi- 

 cated in these three figures, therefore, are the antennal with the largest 

 ventral lobes, the segment of the feeding claws with ventral organs 

 that become much smaller as the embryo develops, and the segment of 

 the slime glands. 



Figure 5 D has been adapted from Kennel and shows a slightly later 

 stage of Peripatus edwardsi. Here the feeding claws and the ventral 

 lobes of the feeding claw segment have withdrawn completely into 

 the oral cavity, the large anterior ventral lobes are the antennal lobes ; 

 those immediately caudad of the preoral cavity are the lobes of the 

 papillar segment. The large dorsal lobe of the oral lips is distinct 

 in this figure. 



At least at the time of their origin the ventral organs show a strik- 

 ing similarity to the developing neural ridges of some beetle embryos, 

 as a study of these figures indicates. However, some significant dif- 

 ferences soon appear. In the first place nerve cells do not form from 

 neuroblasts in the ectoderm as in insects, but instead cells of the 

 organs migrate through the inner "basement membrane" to form the 

 nerve cord, and as they continue through the membrane, the ventral 

 organ shrinks in size and finally disappears. Only those of the an- 

 tennal segment are retained and appear on the under side of the adult 

 brain as the hypocerebral organs (fig. 2 A). 



According to Evans (1902) the brain also includes a pair of an- 

 terior archicerebral lobes belonging to the anterior extremity of the 

 head, and Pflugfelder by means of serial sections was able to demon- 



