Formation of the Digestive Apparatus 307 



iW in'tf V'!r"; ^' '" P-^^^d-S from a crater-like open- 

 ng in the head, through the occiput. The rumen and reticu- 



h^t "II '"f Tl^" '""^ 'P''""^°' f--g"^"^tary shreds indicating 

 that they had been torn away accidentahy or eaten away by 

 some animal before the specimen came into our hands. In this 

 case, the prolapse of the alimentary tract is not lateral, but dor- 

 sal, immediately upon the median line, obliterating for a distance 

 the cerebro-spmal axis. 



Fig. 39. ScHisTocoRMus Fissidorsualis. 

 Showing crater-like opening in the occipital region. 



Since the notochord becomes established prior to the formation 

 of the gut, it would seem improbable that the prolapse would 

 occur through that organ, but rather that it would pass in front 

 of it, and this is apparently what has occurred. A study of Fig. 

 41, /AAand PT, shows that, just anterior to the end of the noto- 

 chord, there is an infundibulum growing down from the thala- 

 mencephalon, or midbrain, while, just opposite, growing upward 

 from the posterior border of the stomatodeum, is the pituitary 

 pouch, which later becomes the pituitary body, the two infundi- 

 buh coming into immediate contact with each other. The 

 fore gut has pushed forward and upward, to escape through 

 this area of low resistance, upon the back of the head. The 

 fore-gut escaping, no neck has developed, and the sternum, ST, 

 extends forward beneath the pharynx, P, and the basi- 

 occipital bone, BS. The illustration from Gurlt hkewise indi- 

 cates a virtual absence of neck, though less pronounced. 



At first the alimentary canal is of the same length as the body 

 and forms immediately beneath the notochord, but later it in- 



