144 PROCEEDINGS OP UNITED STATES NATIONAL MtfSEUM. [18S5. 



bauds pass to the dorsal and posterior wall of the air-bladder, to be in- 

 serted in the median line. Whether this bony column serves to steady 

 the fin in the ace of copulatiou, or whether it serves to give passage to 

 the sperm duct are unsettled questions with the writer. The modified, 

 almost styliform, anal fin of the male measures a third of an inch in 

 length, or nearly one-third of the total length of the fish.* Other pecu- 

 liarities of the male are noticeable, for instance, the more abbreviated 

 air-bladder, which also occupies a more oblique position than in the 

 female. The most remarkable difference presented by the male as com- 

 pared with the female, however, is his inconsiderable weight, which is 

 only 160 milligrams, while that of the gravid female is 1,030 milli- 

 grams, or nearly six and one-half times the weight of the male, an 

 unusual difference in the relative sizes.of the two sexes amongst fishes. 



The adult female, as already stated, is heavier than the male, and 

 measures 1^ inches in length. The liver lies for the most part on the 

 left side. The irftestine makes one complete coil or sigmoid flexure 

 upon itself in the anterior half of the body-cavity ; its posterior third 

 passes back along the floor of the abdominal cavity, and at the poste- 

 rior end of the latter the Wolffian ducts traverse it vertically, to be en- 

 larged near their outlets into a fusiform urinary bladder. 



The ovary is a simple, unpaired orgaii, the greater part of which lies 

 on the right side of the body-cavity below the air-bladder, and serves 

 to fill up the greater jiart of the inferior moiety of the former when de- 

 veloped to maturity with its follicles gravid with embryos. The ova, 

 when full grown, are each enveloped in a sack or follicle supplied with 

 blood from a median vascular trunk, which divides and subdivides as it 

 traverses the ovary lengthwise in a manner similar to that of the stem 

 to which grapes in the bunch are attached. The arrangement of the 

 ova and their attachment to the median vascular rachis is well shown 

 in Fig. 11, Plate VIII, in which the immature ovarian eggs are also rep- 

 resented as small whitish bodies attached to the sides of the vessels. 

 In Fig. 10, Plate VIII, two of these immature ovarian ova are also shown 

 close to ihQ follicular pore of a follicle containing an advanced foetus. 



Every fully-grown ovum, by means of the preceding arrangement, has 

 its own independent supply of blood from the arterial system of the 

 mother, the ovarian arterial trunk being a branch of the median dorsal 

 aorta. Each Q^g and egg-sac is thus supplied with materials for its 

 growth and maturation, the latter eventually becoming specialized into 

 a contrivance by which the lives of the developing embryos are main- 

 tained while undergoing development in their respective follicles. The 

 young or unripe eggs which are found together in the same ovary with 

 the dev^eloping foetuses are, as stated above, enveloped in a cellular and 

 fibrous stroma, which serves not only to strengthen the vessels, but 



*Tlie anal fins of the males of closely allied species of Gamhusia and oi Linda, from 

 Cuba, are similarly modified, according to Prof. Felipe Poey, who has figured those 

 observed by him in his Memorias sobra la Hist. Nat. de la Isla de Cuba, i, pp. 

 382-387, pis. 31 aud 32. Habana, 1851. 



