PISCES. 



1011 



with a similar marsupial apparatus, in which 

 the eggs are hatched and the young permitted 

 to arrive at their full developement prior to 

 their expulsion. These are the Syngnuthida:, 

 or pipe-fishes. There is, however, this remark- 

 able difference between the mammiferous mar- 

 supials and these singularly organized genera, 

 namely, that in the former it is the female that 

 is furnished with the marsupial pouch, whereas 

 in the Syngnathidae the male only is so pro- 

 vided. In fig. 539, representing the male of 

 Syngnathus acus, the marsupial apparatus is 

 well exhibited ; it consists of two large valves 

 () situated beneath the tail, immediately pos- 

 terior to the cloacal orifice. The internal sur- 

 face of this pouch is indented with deep cells 

 (o, 0), more especially towards its posterior 

 surface, where the ova are principally lodged. 

 Here the eggs are hatched, after which the 

 young Syngnathi are retained in the pouch for a 

 considerable period before they are finally ex- 

 pelled. 



In the female Syngnathus there is no sub- 

 caudal pouch developed, but in this sex the 

 vulva is unusually prominent, apparently for the 

 purpose of facilitating the conveyance of the 

 ova into the marsupium of the male. 



In Syngnalhus ophidian (Bloch) the ova, 

 after extrusion from the female and impregna- 

 tion, become attached to the cellular surface of 

 the ventral parietes of the abdomen of the male, 

 but are not protected by cutaneous processes or 

 valves. 



Urinary apparatus. The kidneys in Fishes, 

 as in all other Vertebrata, are two in number, 

 situated on each side of the spine. They 

 are, however, in the class before us remarkable 

 for their very great proportionate size, some- 

 times extending from the anterior boundary 

 of the abdomen quite to its posterior ex- 

 tremity, and occasionally uniting together in 

 the mesial plane, so as to have the appearance 

 of being but a single gland. Internally they 

 present no division into cortex and fasciculate 

 ducts terminating in a pelvic cavity, but their 

 parenchyma is homogeneous, being entirely 

 composed of arborescent ducts, which are im- 

 mediately continuous with the ureters, which, 

 running along the anterior surface of the kidney, 

 receive the uriniferous tubes as they pass along 

 towards the cloaca, where they terminate. Most 

 commonly there is a distinct urinary or allan- 

 toid bladder situated behind or dorsad to the 



rectum (Jig. 539, ./), which, in some spe- 

 cies, is bifid at the anterior extremity, as in the 

 Frog and other amphibia. 



Occasionally the urinary canals unite and 

 terminate by a common duct (ureter) upon a 

 fleshy tubercle or penis-like projection of the 

 walls of the cloaca, as in the female Shark 

 (fg. 538, t), where a bristle is represented in- 

 -troduced into the extremity of the urinary 

 passage. 



Renal capsules, In the osseous Fishes these 

 organs are supposed to be represented by two 

 or sometimes three roundish bodies of a light 

 grey colour, situated sometimes near the mid- 

 dle, oftener at the hinder extremities of the 

 kidneys, at or near the entry of the hremal 

 canal ; sometimes they lie free, sometimes they 

 are imbedded in the renal tissue (Pike, Salmon, 

 Eel) ; but they always possess a proper cap- 

 sule and present a minutely granular texture 

 without distinction of cortical and medullary 

 parts.* In the yellowish suprarenal bodies of 

 the Sturgeon, the granules are minute spherical 

 cells filled by microscopic nucleated corpuscles. 

 In the Plagiostomes they are represented by 

 elongated narrow yellowish bodies situated be- 

 hind the kidneys, and sometimes extending be- 

 hind the dilated ureters. 



BIBLIOGRAPHY. Cuvier, Lemons d'anatomie 

 comparee, 8vo. 1846. Cuvier et Valenciennes, His- 

 toire naturelle dcs poissons, 4to, 1828. Holler, 

 Opera niinora, vol. iii. Monro, Structure and phy- 

 siology of Fishes, fol. 1785. Observations on the 

 organ of hearing in man and other animals, 4(o. 

 1797. Scarpa, De auditu et olfactu, fol. 1789. 

 Cun/paretti de aure interna comparata, 4to. 1789. 

 Hewson, Phil. Trans, vol. lix. Cavolini, Memoria 

 sulla generazione dei pesci c dei granchi, 4to. 1787. 

 Autenrieth, Anatomic de la plie. Wiedeinann's 

 Archiv, torn. i. 1800. Geoff'rui/ St. Hilaire, An- 

 nales des Museum d'Flist. Nat. t. ix. & x. Rosen- 

 thai, Ichihyomische Tafeln, 4to. 1812-22. Spi.r. 

 Cephulogenesis, fol. 1815. Cants, Lehrbuch der 

 Zootomie, 8vo. et 4to. 1818. Erlanterungs-tafeln 

 zur vergleichenden aiiatornie, fol. 1826. Weber, 

 De aure et auditu. Van der Hoeven, Dissertatio 

 philosophy de sceleto piscium, 8vo. 1822. Bakker, 

 Osteographia piscium, 4to. 1822. Meckel, Traite 

 d'anat comp. 8vo. 1828-9. Owen, Lectures on com- 

 parative anatomy, Loud. 1847. 



* Owen's Lectures, (Pisces, p. 285.) 



( T. Rymer Jones.) 



PLACENTA. 



and UTERUS. 



See OVUM (Supplement) 



