Development of the Jugular Lymph Saes. 281 
the blood-contents from the plexiform sac into the systemic veins. 
After the process of evacuation is completed this precardinal con- 
nection is abandoned. It is not possible to state definitely that this 
anterior tap of evacuation invariably develops in all cat embryos, 
but we can state that it occurs with frequency in embryos rang- 
ing between 10.5 and 12.5. mm. in length. (Cf. p. 291.) 
B. VENTRAL VENO-LYMPHATIC PLEXUS. 
1. Cephalic division 
This portion of the ventral plexus (fig. 50) is represented by two 
veno-lymphaties, one of which has fused with the anterior pro- 
longation of the dorsal veno-lymphatic plexus while the other, a 
small dilated sac, fenestrated at its base and still connected with 
the precardinal, lies directly caudal to the anterior tap of evacu- 
ation. 
2. Caudal division. 
A considerable difference is met with on opposite sides of this 
embryo concerning the make-up of this portion of the ventral 
plexus. On the left side (fig. 49) it consists of a single, irregular 
sac which communicates with the promontory by a single opening 
(Tap B, fig. 49). On the right side (fig. 50) it is composed of two 
entirely detached and independent sacs and of a portion whieh still 
communicates with the systemic veins at three points. 
The two detached and independent sacs are completely closed 
and, as far as we can determine under a high magnification, do 
not communicate with the venous svstem. The anterior and 
Jarger of the two sacs is irregular in form and lies on the lateral 
surface of the preeardinal and promontory near the promontorio- 
precardinal angle. In its form and position it closely resembles 
the caudal division of the ventral plexus on the left side of the 
embryo (fig. 49). It contains no blood corpuscles and from a 
histological standpoint cannot be distinguished from a typical 
lymphatic structure. The other closed sae lies upon the lateral 
surface of the promontory, slightly dorsal and caudal to the first 
and between the latter and the anlage of the cephalic vein. This 
sac still contains a large number of blood corpuscles. 
