ON THE FOETAL MEMBRANES OF CHELONIA. 



29 



three are from the region of the remnant of the posterior tube of the 

 amnion, Fig'. 78 beinc; the most anterior, and in order to facilitate 

 the imderstandini>- of these sections, I have introduced a diagram of 

 this region in Fig. 77. In this diagram, the serous envelope is 

 represented as spread over all the structures ; the amnion is below it 

 and is indicated <wly by the line from which the sero-amniotic con- 

 nection arises. The remnant of the posterior tube of the amnion has 

 before this stage been modified into a solid eompressed string of 

 (•('lis and is shown l)y the hea\iest dark line whioli stretches from 

 tile amnion to the serous envelope. The sero-amniotic connection 

 is r('])resent('d shaded by parallel dotted lines. Throughont the 

 largest ])art of its length (froîii its anterior end to near its posterior 

 end) this structure lies in one plane and is sinijily a membrane stretch- 

 ing between the amnion and the serous envelope. Bnt on coming to 

 the r(^gion of the posterior tube (^f the amnion, it makes a sudden 

 turn of over 90° to the left and goes to the serous termination <>f the 

 posterior tu1)e, wliicjh latter structure it connects (m its way with the 

 serous envelope. It will of (jourse be undersiood that the sero- 

 amniotic connection from its anterior to its posterior end was 

 originally in one straigiit line and that its |)C(MiIiar bent termination 

 at this stage was Iii'ouglit about bv its a('(;oin|)an ving the posterioi* 

 anuiioti(.- tube in all its (.•liang(\s of r(îlîtti\(' position. It is this 

 peeidiar bent pai't of tlie s(M'o-amniotie (Connection wliich is seen as 

 the ti'iangidar white ])atch at the dorsnl end of t he sero-:unniotic 

 seam. (Figs. (18, 61), 71, IM. \'T[l.). 



Fig. 78 is from the regi'^'i '*f ^'i^' simple sero-amniotic connection 

 (the line 1-1 in Fig. 77). in such a section, the sero-amniotic con- 

 nection is regally a striking structure, forming a broad and con- 

 spicuous connecti(W lietween the serous envelope and the amnion. 

 The e])il)last cells in it are now very flat and closely packed. riie 



