66 K- MITSUKURI; 



iiotochord show signs of fusion by the presence of some 

 spiudle-sliaped celJs in the bonndary between the two. 



C is two sections behind h. The enteren, though still open, 

 is narrowing. The medullary chord and the notochord 

 are now nearly fused. 



d is next to c. The enteron is; closed below, and shows a 

 partial division into the u])]'er enteron proper and the 

 lower allantoic cavity. 



e is next to d. The division is now complete. 



f is next to e. The cavity has disa]>]'eared from the aljan- 

 tois. 



g is next to /. The noto-medullary-chord sliows signs of 

 fusion Avith the wall of the enteron. The mesoblast on 

 each side of the enteron is fused witli the posterior con- 

 tinuation of the allantoic mass. The coelom has gone 

 across. 



h is two sections behind // and is very much like that 

 section. Only the epiblast has nearly encircled the tail 

 which is unenclosed only in the ventral median line. 



i is two sections behind //. The tail is now entirely en- 

 circled by the epiblast and lies free in the amniotic 

 tube. At the point where the epiblast of two sides met 

 last in the median ventral line of the tail, the epiblast is 

 fused with the mass within. This is evidently a part of 

 the primitive streak. The cavities of the enteron and the 

 medullary chord are united as the neurenteric canal. 

 The lower part of the enteric wall is fused with the in- 

 ditferent cell-mass. In the amniotic tube surrounding 

 the tail, the epiblast is clear all around of the mesoblast 

 lining it, and thus there is no primitive streak here. 

 j is three sections behind /. The enteron has become lost in 

 the indifferent cell-mass and only the medullary chord is 

 still persistent, although the lower part of its wall is al- 

 ready fused with the indifferent blastema. The {)rimitive 

 streak is still present in the ventral median line of the tail. 



