Text-book of comparative anatomy . laseminis, which lie at the 2 sides of the mid-gut, enterthe most anterior end of the vagina at the point wherethe oviducts join it. Male Apparatus (Fig. 376, E).—The testes arepaired or unpaired tubes placed like the testis or testes are continued anteriorly intoan unpaired efferent division, which has beenregarded as a seminal vesicle. This vesicula semi-nalis divides anteriorly into 2 canals, the vasadeferentia, which encircle the oesophagus. Each vasdeferens ends in a male copulatory apparatus. Themale genital aperture common to the 2 copulatory
Text-book of comparative anatomy . laseminis, which lie at the 2 sides of the mid-gut, enterthe most anterior end of the vagina at the point wherethe oviducts join it. Male Apparatus (Fig. 376, E).—The testes arepaired or unpaired tubes placed like the testis or testes are continued anteriorly intoan unpaired efferent division, which has beenregarded as a seminal vesicle. This vesicula semi-nalis divides anteriorly into 2 canals, the vasadeferentia, which encircle the oesophagus. Each vasdeferens ends in a male copulatory apparatus. Themale genital aperture common to the 2 copulatoryapparati lies, in contradistinction to that of thefemale, in the anterior portion of the body, betweenthe 2d pair of hooks. Corresponding with the recep-tacula seminis of the female there are in the male 2blind tubes running backward, these are apparentlyorgans for propelling the semen, and enter the 2 spermducts. The end of each sperm duct enters a very longchitinous cirrus, which at a time of rest is rolled upin a special IX. Ontogeny. FIG. 378.—Female of Pentas-tomum taenioides at the time ofcopulation, with the viscera (afterLeuckart). h, Hooks; oe, oeso-phagus ; rs, receptacula seminis,one of which is still empty; rf,gut; or, ovary ; va, vagina. We can only bring forward a few facts concerningthe ontogeny of the Arachnoidea, chiefly such as areof most importance from the point of view of compara-tive anatomy. 1. The segmentation is in the main that of the centre- or mesolecithal eggs. Ablastoderm is formed covering the yolk, in which, however, merocytes remain. Theformation of the germ layers and of the rudiments of the most important organsproceeds, as in other Arthro2)oda, from a blastoderm plate, which may be called theembryonic rudiment. In the Scorpionidce, however, the egg seems to be meroblasticallytelolecithal, and the furrowing takes a corresponding course, so that no blastodermenveloping the yolk on all sides is formed, but a germ disc is developed at o
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
