gg K. MITSUKURI; 



in the part of the priinifive streak which persists, as will l)e seen in 

 the next series. 



In the elongation of tlie tail, various structures are developed in 

 sita from the inditterent " Eudwulst" cell-mtiss. Of these, the medul- 

 lary chord is formed first ( /), and tlien the enteron and the noto- 

 chord ure. differentiated (,/-/), nlthough the lowest part of the enteron 

 is fused with the indifferent tissue for s()ine time after the rest has heen 

 formed. The mesohlast is nlso formed from tlie indifferent tissue. 



Series XIV. 



(PI. XL) 



Chelotda caonana. 



A quite adcdnccd tiuhnjo taken out 16 chiifs after deposition ; witlt 

 ficc (lill-slits all foniied, iritli tlie cranial flexure well niarlicd, witli the eijes 

 and ears alreadi/ quite adc((Nced, and uutli tlie appendacfes present as hnobs. 

 About the sta.<je of Fiijs. 11 and lia, Contrih. II. The allantois appears 

 in tlie bodij caritij as a siiuill vesicle. (^"^*) 



This series is introduced to show the relations of different parts 

 in the posterior part of an advanced emhryo, and to show the form- 

 ation of the proctodicum. 



a is from the posterior dorsal region. The aJlantois is sepa- 

 rate from the emhryo proper. 



b is three sections behind <(. The allantoic mass has nnited 

 with the body proper (hi the left side. 



C is four sections beliind b, whicli it very much reseml)les. 



d is seven sections behind c. The allantoic mass is now 

 united Avith the body proper on both sides. The allantoic 

 cavity is gradually approaching the enteron. 



e is three sections behind d. The epiblast is gradually 

 enclosing the body proper. 



