Page:The New International Encyclopædia 1st ed. v. 17.djvu/58

* KEPRODtrCTIVE SYSTEM. 42 the Cliordntn, wo find that in Biihinof;lossu9 the sexes arc sc|iiuiite, and the oviiries and testes are H row of siicular organs which open to the ex- terior hy a series of pores, or, in the American species, by rupture. Tunicatcs are hermaphro- ditie. Jn Amphioxus tlic sexes are separate. The sexual organs are liorseshoe-shaped sacs which lie in '2li pairs and without ducts. The ova and spermatozoa burst the atrial cavity and reach the exterior by means of the atropore. The se.xes of the lamprey are separate and the sexual or- j;an is unpaired. The sexual i)ro;nation is internal in all the sharks except the Greenland shark. The claspcrs act as iutromittent organs. With a few excep- tions, such as Ihe dogfish, there are two ovaries and the oviducts arc separate from the ovaries. The oviducts, the Miillerian ducts, are united an- teriorly and open into the liod' cavity. The eggs are extruded into the body cavity and then pass into the oviducts. There is a large shell gland in the oviduct. The majority of fishes lay eggs that are fertilized outside the body. Jlost sharks and a few teleosts are viviparous, the eggs being hatched in the oviduct or ovary. In two of the sharks the yolk-sae and the wall of the oviduct are united, suggesting the placenta of mammals. The ovaries of teleosts are continued backward into a duct. Posteriorly the two ducts fuse. The oviducts of the Dipnoi are somewhat coiled, like those found in Amphibia : each connects with the body cavity near the pericardium by means of a funnel-shaped aperture. Hermaphroditism is not uncommon throughout the Teleostei. KErTiLE.s .KD Birds. The ovaries are broad in the ttirtles. and long and narrow in snakes and elongated lizards. The ovaries are usually asym- metrical. Only the left ovary is completely de- veloped in birds. The oviducts open into the ab- dominal cavity liy wide funnel-shaped apertures and in the walls of the ducts are glands for the formation of albumen and egg-shells. The ovaries, like the testes, increase in size during the breed- ing season. In birds the vas deferens, like the ovaries, opens into the cloaca by an independent apertnre. In lizards it fuses "with the ureter. There is a copulatory organ in reptiles; in birds it exists onl.y in the ducks, geese, and Ratitie. The genital apparatus of mammals lies in the lumbar and pelvic .regions. When the ova are mature they pass into the body cavity or are im- mediately caught up by the funnel-shaped opening of the oviducts. This portion is known as the Fallopian tubes. In the majority of mammals the oviducts fuse behind the Fallopian tubes to form the uterus. It is in the uterus that the ova attach themselves to the maternal tissue and de- velop. The fused region behind the uterus is known as the vagina. In moiiotremes the Jliil- lerian duct remains distinct and there is a cloaca. In marsupials the Miillerian duct begins to fuse to form a vagina. In most other mammals an anterior fusion of the two parts of the uterus occurs. The degree of fusion varies in different species. In Primates the only evidence of the paired origin is seen in the Fallopian tubes. The testes"of mammals develop in the same position as the ovaries. I)ut they later pass out of the abdominal K.EPTILE. cavity through an opening in the latter known as the inguinal canal, and descend into the scrotal sacs; but in many mammals the testes remain permanently in the abdomen. External genital apparatus exists as follows: In elasmobranchs there are male 'clasjiers' wltich are inserted into the cloaca and oviduct of the female. In connection with them there is a gland which is histologically much like the luopygial glamls of birds. In Ampliibia the male of (Jym- nojdiiona alone possesses an eversible cloaca. In lizards and snakes there are two erectile penes outside the cloaca. Each is furrowed. Organs of similar nature, but much less develojied, occur in the female. Clielonians and crocodiles have a copulatory organ united with the ventral wall of the cloaca. It is made up of two fibrous fused masses, and, as in the above copulatory organs, is regulated by well-dcvelojied muscles. There is a furrow on its surface. The female also has a median, less well developed organ of the same character. In most Ratitie and some Carinatie there is an eversible tube strengthened by two fibrous bodies. When at rest it is coiled up in the left side of the cloaca. The copulatory organ of monotremes lies between the urinogenital sinus and the cloaca, and is fused with the ventral wall of the latter. In all other mammals the organ arises on the ventral wall of the cloaca. In the female it is channeled. In the male the groove is closed to form a canal. Three bodies of erec- tile tissue are developed in connection with the penis of man. The greater part of one of these glands occurs at the apex of the penis and is known as the glans penis. The clitoris of the female is the homologue of the male penis. , Consult: Lang, Text-Book of Comparative An- atomy (London. 1891-96) ; Wiedersheim, adapted by W. N. Parker, Compuratiie Anatomy of Ver- tebrates (London, 2d ed., 1897). EEPTILE (Lat. reptile, neu. sg., se. animal, animal, from rcptilis, crawling, from repere, to crawl ; connected with serpere, Gk. Ipiruv, her- pein, Skt. sarp. to creep). A cold-blooded verte- brate animal of the class Reptilia, breathing by lungs and having a single median occipital con- dyle. In their larger, phylogenetie relationships, reptiles occupy a central position, but are close- ly in aftinity with birds, so that the two classes were united by Huxley into a group, Sauropsida, in distinction from the Mammalia and from the Ichthyopsida, or amphibians and fishes. "On the one hand," Gadow asserts of the reptiles, '"there is not the slightest doubt that they are evolved from some branch of the Stegacephali. whilst on the other hand the reptiles, probably through some branch of the Theromorpha, have given rise to the mammals; some other reptilian branch, at ])resent unknown, has blossomed out into the birds." Cl.ssification. The history of the develop- ment of the ideas on the classification of reptiles is given under HERPETOLOGy (q.v. ). The ar- rangement by Parker and Haswell is as follows: Class Reptilia: Order I. Squamata. — This includes the Laeer- lilia (lizards), Ophidia (serpents) . and Pythono- morpha (extinct snake-shaped forms, with pad- dle-like limbs and lizard-like slaills). Order II. Rhyncocephalia. — Lizard-like rep- tiles, often huge, scaly, with walking limbs; ver- tebrsE amphicoelous ; sacrum composed of two