358 THE AMERICAN NATURALIST. [Vor. XXXIX. 
Examination of a number of skates which had been injected 
(by students) with starch or a starch-gelatin mixture (see Rand, 
:05) brought to light several animals in which the rectal 
venous network had been more or less completely filled from 
the cardinal sinus. In these cases, the lateral vein had been 
injected forward, but not backward. The cardinal sinus had 
do. JE 


Fic. 3.—Showing the relation found in Case VI between the posterior end of the lateral vein 
Ath A 1 1 

Th 1 1 f +h 

but the rectum is twisted through 90° 
* D r ’ 
so as to bring into view the right side of its anterior region as well as the right side of 
the rectal gland and mesorectum. 
C ti ( 1 CERT - 

. g the rectum at a-a. 
ap. clc., cloacal aperture ; cZc., cloaca; g/.rt., rectal gland ; »s'7?., mesorectum; ref. vn., ven- 
ous network on cloaca and rectum; rZ., rectum; sz. cr., rectal prolongation of cardinal 
sinus ; Un., veins connecting rectal venous network with cardinal sinus; vz. /., lateral 
vein. 
filled from the precaval (Cuvierian) sinus and the mass had 
made its way back through the rectal extension of the cardinal 
sinus into the rectal network. This network, therefore, may be 
injected either from behind, by way of the lateral vein, or from 
before, by way of the cardinal sinus. Figure 4 shows the lat- 
eral vein in its entire extent, with its connections as found in 
our injected skates. 
