pis ah - ay 2 
THE CYPRINODONTS. 75 
gestive of what obtain in young of Rivulus and Gambusia. As a whole the 
circulation of the bag amounts to what in the adult would correspond to the 
sinus emptying into the auricle, with the possible addition of a portion of 
the ventral cutaneous vein. As worked out from the specimen at hand, a 
vessel sent down from the cardinal just behind the gills at each side, passes 
at the side of the heart, to the upper edge of the bag, where, as it extends 
backward, it sends downward branches which branch again and again, then 
converge and unite toward the point, near the middle of the lower surface of 
the sac, at which they discharge their contents, with what has been added by 
the papillw, into a vein or sinus (Plate VI. Fig. 1, 3, ss) that lies free from 
and within or above the walls of the bag and runs forward and up to the 
auricle, into which it discharges. Beside the two anterior supply vessels 
another passes down from the main vessel above the bladder, below the verte- 
bra, to the left side of the vent below which it forks and sends a branch for- 
ward along the upper edge of the bag at each side (Fig. 1, s’, Fig. 7.) The 
branches and branchlets of this vessel are similar to those of the anterior 
portions of the bag, and they discharge into the same vessel (Plate VI. Fig. 
1, 3, ss). At this stage the auricle lies below the ventricle (Fig. 12, 13). 
As the bag atrophies the anterior vessels (s, in Fig. 12) at each side of the 
auricle unite with the median (ss, of the same figure) to form the sinus 
emptying into the auricle (s, in Fig. 10, 11). The lateral vessels of the 
upper edge of the bag apparently give way to the ventral cutaneous vein. 
The branchlets and the long median vessel (ss) are absorbed with the bag 
itself. In the change to the adult condition the auricle and ventricle change 
places so that the latter eventually lies lower than the former, though not 
directly below it. The heart of the young is outlined on Plate VI. Fig. 6, 
12-14, and that of the adult in Fig. 10,11. The bladder also undergoes 
considerable changes in the young Anableps, as may be seen by comparison 
of Plate VI. Fig. 1 (4), with Plate VII. Fig. 6, 11-15. 
Valenciennes, 1846, XVIII, 259, Atlas, pl. 539, has described and figured 
the bladder of the male of Anableps, but from a very imperfect understand- 
ing of the structure. He ignores the muscular valve at the junction of the 
seminal and urinary ducts (z, in Plate VII. Fig. 6, 11-15), a structure which 
represents the external openings of the ancestral form, and he says that 
urine and semen are discharged into a common receptacle, “ Les uretéres 
sont deux longs tubes gréles, attachés aux reins dans presque toute la lon- 
gueur du viscére. Ils se terminent dans ce poisson tout autrement que 
