Plate XVI. 



(For explauatiou nf ;il)lirt'viiitious aud colours see ]■. ;i7()) 



i'lGs- 22-36 : — These are surface views of tJirec eggs aged respectively 812, 385, 

 and 432 hours. They are arranged mostly in three horizontal rows, each 

 row being devoted to o]ie egg. The first two coloured figures of a row are 

 the surface views of opposite faces of the same egg, taken out from its non- 

 cellular envelopes, and the two last figures of a row are the outlines of the 

 foetal membranes of the corresponding faces. In following a blood vessel or 

 any other structure from one face to the other in these rows, it should be 

 remembered that the lower edge of the first and third figures of a row 

 should be applied to the upper edge of tlie second and fourth figures. 

 It should also be noticed that as an egg has a considerable thickness, a 

 structure leaving one face m;i,y not be found entering at exactly tlie corres- 

 ponding point of the other. Each of Figs. 26, 81, and 36 represents the 

 allantoic septa, come together at the vegetable pole of the respective egg, 

 as seen from that pole. P\-ill lines are tracings of the septa on the outer 

 limb of the allantois. In Figs. 27-28 and Figs. 32-33, the ijranciies of 

 the allantoic vein are anastomosed. In the example given in Figs. 32-36 

 the interahantoic septum is not folded on itself. In these examples of later 

 stages the interallantoic septum is not intluenced by tlie left allantoic artery. 

 The sero-amniotic eon])ection of the specimen represented in — 

 Fig. 22-2(> is ri'prescïjited ;i|);ii-t in Fig. 51, 

 „ '^7-Hl „ „ „ 54, 



,. o2-3<i „ „ „ 56. 



Fig. 87 ; — iJorsai view of tlie \icinity of the sero-amniotic coimection of an embryo 

 in the same stage as that represented in Fig. 7. Tlie dotted lines show the 

 extension of the lateral fold formed within the amniotic cavity (see Diag. 5). 

 The points A, B, &G correspond to those marked with the same letters in the 

 section (Fig. 92) of that level. The blood vessels in the inner allantoic limb 

 are for the sake of simplicity not represented. 



Figs. 38-42: — Dorsal views of the sero-amniotic connection represented in Figs. 1. 

 2, 3, 4, and 5 respectively. The partly obliterated mesoblastic septuin is 

 represented by a broken line. All are magnitied to the same scale ( x 10). 



