438 MALL. [Vox. XII. 
formation of the coelom confirms this statement. As the first 
blood-vessels are formed, lymph vessels appear on their dorsal 
side, which flow together to form a network, and accompany the 
primitive veins to the axial part of the germinal area. Here 
the lymphatics form two spaces, one on either side of the body, 
which soon unite across the body on the ventral side of the 
heart. In this way the primitive body cavity of birds appears 
at first as an H, the uprights of which are on either side of the 
body and the cross-piece on the oral side of the sinus venosus. 
In its further development the sinus venosus grows to the dorsal 
side of the cross-piece, thus reversing the relation of the vascular 
system to the coelom in this portion of the embryo. The 
uprights of the H fall to the outside of the body, and are 
swallowed up in the formation of the amniotic folds. 
According to Budge two diverticula grow from the cross- 
piece of the H, one on either side of the chorda, towards the 
tail of the embryo, to form the 
primitive pleuro-peritoneal 
cavities. Budge’s paper was 
published from fragmentary 
notes after his death, and I 
am sure that the above state- 
ment is not correct. Profes- 
sor His has placed at my 
Fi Scot ek or Giese disposal Budge's specimens, 
Coelom. Although the embryo has been injected, which J think show conclu- 
the injection masses @ and c are not continuous. sively thar iis interrec tion 
of this subject is not correct. Most of the injections were 
made into the amniotic fold, which is very large in birds. 
Cross-sections of chicks at this stage show that the large extra- 
embryonic coelom communicates very freely with the body cavity, 
and the cross-piece also communicates freely with the cavity at 
the anterior end of the embryo. This has already been described 
and pictured by Cadiat,! and recently again by Duval.?, Around 
the heart, however, the communication is freest between the 
extraembryonic coelom and the body cavity, and it is natural 

1 Cadiat: Jour. de l’Anat. et de la Physiol., 1883, Plate V, Figs. 1 and 2. 
2 Duval: Atlas d’Embryologie, Plate XXII, Fig. 354. 
