PROTOTR ACHE ATA. 



FIG. 170. VENTRAL VIEW OF THE 

 HEAD OF AN EMBRYO OF PERIPATUS CA- 

 PENSIS AT A LATE STAGE OF DEVELOP- 

 MENT. 



/. thickening of epiblast of procepha- 

 lic lobe to form supra- oesophageal gan- 

 glion ; m. process from procephalic lobe 

 growing over the first post-oral appen- 

 dage ; o. mouth; e. eye; i and 2, first 

 and second pair of post-oral appendages. 



bases become gradually closed over by two processes of the 

 procephalic region (fig. 170, m) 

 The whole of these structures 

 assist in forming a kind of 

 secondary mouth cavity, which 

 is at a later period further 

 completed by the processes of 

 the procephalic region meeting 

 above the mouth, covering over 

 the labrum, and growing back- 

 wards to near the origin of the 

 second pair of post-oral appen- 

 dages. 



The antennae early become 

 jointed, and fresh joints con- 

 tinue to be added throughout 

 embryonic life ; in the adult 

 there are present fully thirty 

 joints. It appears to me probable (though Mr Moseley takes 

 the contrary view) from the late development of the paired 

 processes of the procephalic lobes, which give rise to the circular 

 lip of the adult, that they 

 are not true appendages. 

 The next pair therefore 

 to the antennae is the first 

 post-oral pair. It is the 

 only pair connected with 

 the mouth. At their ex- 

 tremities there is formed a 

 pair of claws similar to 

 those of the ambulatory 

 legs (fig. 171). The next 

 and largest pair of appen- 

 dages in the embryo are 

 the oral papUlae. They 

 are chiefly remarkable for 

 containing the ducts of the slime glands which open at their 

 bases. They are without claws. The succeeding appendages 

 become eventually imperfectly five-jointed ; two claws are 



FIG. 171. HEAD OF AN EMBRYO PERIPA- 

 TUS. (From Moseley.) 



The figure shews the jaws (mandibles), and 

 close to them epiblastic involutions, which 

 grow into the supra-cesophageal ganglia. The 

 antennae, oral cavity, and oral papillae are also 

 shewn. 



