THE DEVELOPMENT OF PERIPATUS CAPENSIS. 
461 
the appearance of the appendages and of the lip-fold which 
encloses the jaws in the adult, and of the eyes. 
The appendages arise as hollow processes of the body wall, 
containing prolongations of the somites. The first to appear 
are the antennae, into which the praeoral somites are pro- 
longed. The remainder appear from before backwards in 
regular order, viz. jaws, oral papillae, legs, 1, 2, . . . 17, and 
the rudimentary anal papillae, which are the appendages of 
the last, i. e. the twenty-first somite. 
The full number of somites and their appendages is not, 
however, completed until a later stage, the posterior being the 
latest to appear. 
The eyes appear in this stage as invaginations of the sides of 
the nervous thickenings (the future supracesophageal ganglia) 
of the praeoral lobes (fig. 29, e). The invaginations are at first 
shallow, but soon become deeper, and in the next stage con- 
verted into closed vesicles, the front wall of which (i. e. the wall 
next the skin) forms the epithelium outside the so-called lens 
of the adult eye, while the internal wall thickens, and remains 
continuous with the cerebral ganglion, and gives rise to the 
retina. The enclosed vesicle persists, and apparently becomes 
filled by the structureless lens of the adult eye, if the struc- 
ture described as such be not a mere coagulum produced by 
reagents. The eye of Peripatus is therefore a cerebral eye. 
The lips. — The end of the spiral stage is also characterised 
by the appearance of the buccal fold or fold which encloses the 
jaws and buccal cavity, and so constitutes the tumid lips of the 
adult. This is a fold of the side walls of the body immediately 
outside the jaws, and extending from the praeoral lobe of its side 
to just behind the jaw. It is at first most marked in front, 
which fact led Moseley to describe it as a backward process of 
the praeoral lobe. 
The first indication of the lip is shown in fig. 29, just behind 
the eye ; it is seen better, however, in the figure of the next 
stage (fig. 30, L). 
This stage is also characterised by the fact that the anus has 
shifted to the hind end of the body (the primitive streak 
