TRACHEATA. 



383 



cords with imperfectly marked ganglia, and the nephridia (seg- 

 mental organs 1 ), would render its embryology of peculiar in- 

 terest. Unfortunately Moseley was unable, from want of 

 material, to make so complete a study of its development a~S of 

 its anatomy. The youngest embryo observed was in part 

 distinctly segmented, and coiled up within the egg (fig. 168 A). 

 The procephalic lobes resemble those of the Arthropoda gene- 

 rally, and are unlike the prae-oral lobe of 

 Chaetopods or Discophora. They are not 

 marked off by a transverse constriction 

 from the succeeding segments. The three 

 embryonic layers are differentiated, and 

 the interior is filled with a brownish mass 

 the remnant of the yolk which is pro- 

 bably enclosed in a distinct intestinal wall, 

 and is lobed in correspondence with the 

 segmentation of the body. The mouth 

 invagination is not present, and but two 

 pairs of slight prominences mark the rudi- 

 ments of the two anterior post-oral ap- 

 pendages. 



The single pair of antennae is formed 

 in the next stage, and is followed by the 

 remaining post-oral appendages, which 

 arise in succession from before backwards 

 somewhat later than the segments to which 

 they appertain. 



The posterior part of the embryo be- 

 comes uncoiled, and the whole embryo 

 bent double in the egg (fig. 168 B). 



The mouth appears as a slit-like open- 

 ing between and below the procephalic 

 lobes. On each side and somewhat behind it there grows out 

 an appendage the first post-oral pair (fig. 169, i) while in 

 front and behind it are formed the upper and lower lips. These 

 two appendages next turn inwards towards the mouth, and their 



FIG. 169. EMBRYO 

 OF PERIPATUS CAPENSIS. 

 Slightly older than A in 

 fig. 168; unrolled. (After 

 Moseley.) 



a. antennae ; o. mouth ; 

 i. intestine ; c. procephalic 

 lobe, i, 2, 3, etc., post- 

 oral appendages. 



1 F. M. Balfour, "On certain points in the Anatomy of Peripatus capensis." 

 Quart. Joitrn. of Micros. Science, Vol. xix. 1879. 



