ox THE FOETAL MEMBRANES OF CHELOXIA. OO 



tlie \eijti-al sfide is gi\ eii in Fig. 7o (1*1. \'JII.). The allautoi.s ha.s 

 covered a larger j)arl of the yulk >a<'. lea\ iug ojiIn an oxal .s|»ace at 

 the lower [)n\r mieovered. Thi.s o\al .space i.s hounded anteriorly hv 

 the sero-aniniotic connection hent hke the letter \ , and from tliis is 

 seen stretching" tbrwai'd tlie anterior prolongation of the amnion 

 whicli unites the main portion of the latter with the sero-amniotic 

 connection (Comp. J)iag. VIL. IM. X.). The two constrictions or 

 meseuterydike folds of tlie allantcjis caused by the two sets of 

 blood-vessels are also seen distinctly in the tigure. 



The final shape <jf the fœtal membranes is seen in Tig. 74 (1^1. 

 \ Jli. Comp. Diag. V'JL, PI. X.), and tliat part of the ventral surface 

 where the lobes of the allaiitois finally meet is represented in a more 

 enlarged scale in J: ig. 81 (1*1. IX.). The space left uncovered by the 

 allcintois in Tig. 78 is now mostly grown over by the growtli from the 

 posterior side. There is however a small space still left uncovered 

 by the allantois. It is triangular in shape; the apex of this triangle 

 is bounded anteriorly by the sero-amniotic connection, now com- 

 pressed to an irregidar horse-shoe shaped opaque streak. On two 

 sides of the triangle is the anterior allantoic lobe (which equals the 

 middle and left lobes): posteriorly, it is limited by the posterior 

 allantoic lobe (which e({uals the right lobe). From the lateral angles 

 of this triangle the mesentery-like fold of the allantois stretches on 

 each side to each set of the allantoic vessels. These correspond to 

 the two notches in F^ig. 72. The view fr<jm inside of this reofion 

 is given in FTg. Sla. In this there is a ridge across the middle of 

 the triangular area. This is the line of junction of the yolk-sac and 

 the amnion, as will become clear from the sections to be described 

 directly. It appears in the external view as an opaque line across 

 the horse-shoe shaped sero-amniotic connection (F'ig. 81). The 

 anterior [n'olongation of the amnion connecting the main body of 



