430 RANDOLPH WEST 



phatic plexus may be clearly seen to occupy the area which in 

 the reconstruction of the 11 mm. chick was filled only by iso- 

 lated mesenchymal spaces. A great number of these isolated 

 spaces (yellow, 8) still exist, not connected as yet with the lym- 

 phatic plexus. They occur in greater numbers medial to the 

 lymphatic plexus which is connected with the veins (green, 10) 

 that is between it and the caudal muscle plate, than they do 

 lateral to the lymphatic plexus, although quite a number, as 

 may be seen from the figure, occup}^ the latter position. It is 

 especially interesting to note that the isolated spaces lie on all 

 sides of the lymphatic plexus, seeming to precede it and form 

 in an area which an hour or two later is occupied by the con- 

 tinuous plexus of lymphatics, connected with the coccygeal 

 veins. Such outlying isolated spaces are clearly shown at the 

 cranial end of this reconstruction. 



Fig. 12 Reconstruction of caudal vessels of a chick of 11 mm., Series 20. 

 X 150. Antro-lateral view; arteries in black; veins and capillaries in white; 

 isolated spaces in yellow. 



Fig. 13 Reconstruction of caudal vessels of a chick of 14 mm., Series 17. 

 X 150. Antro-lateral view; arteries black; veins and capillaries white; lym- 

 phatic plexus connected with veins, green. The disconnected mesenchymal 

 spaces have been omitted from this reconstruction. 



Fig. 14 Reconstruction of caudal vessels of a chick of 15 mm. Series 16. 

 X 150. Antro-lateral view; arteries black; veins and capillaries white; lym- 

 phatics connected with veins, green; mesenchymal spaces yellow. 



Figure 12 9b, Lateral branches of coccygeal vein 



3, Coccygeal vein draining lymphatics only 



4, Coccygeal artery ^^' Lymphatic plexus connected with 

 8, Mesenchymal spaces (green) *^^ ^^^^« ^S^^^^^ 



,9, Lateral branches coccygeal veins ^^' Postcardinal veins 

 draining haemal capillaries 



Figure 14 



Figure 13 a r^ i ■ 



^ 3, Coccygeal vein 



3, Coccygeal vein 4, Coccygeal artery 



4, Coccygeal artery 8, Disconnected mesenchymal space 



5, Haemal capillary plexus 9, Lateral branch of coccygeal vein 

 .9, Lateral branches of coccygeal vein 10, Lymphatic plexus connected with 



9u, Lateral branches of coccygeal veins veins 



draining haemal capillaries and lym- 11, Aorta 

 phatics 18, Postcardinal vein 



