72 THE CYPRINODONTS. 



the upper side of the orbit for the protection of the eye. In the bases of 

 the pectorals the carpal elements are nearly obsolete, those remaining are 

 very small ; the clavicula and other coraco-scapular bones are thin and 

 broad, but strong and firmly attached. Posteriorly the two processes of 

 the hindmost vertebra form a fan of medium size, in which the line of 

 junction is distinct. All of the species in the genus, as known at present, 

 have a convex posterior margin to the caudal fin. The halves of the 

 pelvis are widely separated. More than half of the length is occupied 

 by the body cavity. 



In its earlier stages the young Anableps bears some resemblance to Rivu- 

 lus. At this time the eye is not traversed by the band of the conjunctiva, and 

 the pupil is not divided by projecting lobes of the iris. The eyes are not 

 very prominent above the crown ; the latter is arched. The dark band 

 across the cornea, the bony shield above the orbit, and the lobes in the pupil, 

 dividing it into an upper section and a lower, are of later appearance. A 

 peculiar feature of the embryo is the abdominal pouch, or bag, containing 

 the intestines, below the permanent ventral walls. This pouch gives the em- 

 bryo of Anableps an outline similar to that of Gambusia (see Plate VI. Fig. 1). 

 It extends from the shoulder girdle to the vent, separates the ventrals perma- 

 nently, and communicates with the body cavity by a slit that extends from 

 the vent forward nearly to the coraco-scapular arch. Its surface bears nu- 

 merous lines of more or less confluent papillse, converging from the body 

 downward to a point near the middle of the lower side. These papillte 

 mark the courses of the blood vessels from which they rise and into which 

 they pour the food supply drawn from the portion of the egg remaining with 

 the embryo inside the egg-envelopes. Near the heart, near the vent, and 

 around the lower point of convergence the papillae are larger, in cases unit- 

 ing and forming continuous ridges. Possibly in addition to their absorbent 

 function they also serve a purpose in oxygenating the blood. They persist, 

 after the egg envelopes are ruptured, for a time, until the young in the 

 ovarian chamber have reached a length of about two inches ; then the sac 

 becomes thin and with the papillae is itself absorbed. The yelk is exhausted 

 by the time the embryo has attained a length of half an inch ; the continued 

 growth of body and sac is, within the egg coverings, nourished from the 

 included albumen, or later, from the liquids by which the sac is surrounded 

 in the cavity of the ovary. After the fish has nearly completed its pre- 

 natal development the intestines gradually withdraw from the bag into the 



