File:Text-book of comparative anatomy (1898) (14756346946).jpg

Identifier: textbookofcompar01lang (find matches)
Title: Text-book of comparative anatomy
Year: 1898 (1890s)
Authors: Lang, Arnold, 1855-1914 Bernard, Henry Meyners Bernard, Matilda Haeckel, Ernst Heinrich Philipp August, 1834-1919
Subjects: Anatomy, Comparative
Publisher: London, New York, Macmillan and Co.
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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nd testes, andripen when floating freely in the ccelomic fluid. From this they aredischarged through nephridia which are more or less strongly modified 262 COMPARATIVE ANATOMY CHAP. at the time of sexual maturity, or through nephridia which arepermanently transformed into genital tubes. In Stcrnaspis, in the female one ovary is found, and in the male one testis. Thegenital gland in both sexes has the form of a four-lobed pouch, which lies betweenthe loops of the intestinal tube, and passes into 2 efferent ducts opening outwards,between the 7th and 8th segments. The genital products do not enter the bodycavity, but pass from the cavity of the genital gland to the exterior through theefferent ducts. The cpaestion as to whether these ducts represent modified nephridiamust be decided by further research. The Mysostomidce (Figs. 175 and 176) are hermaphrodite. Theirsexual apparatus does not easily admit of comparison with thatof the other Annulata, but rather recalls in many points that of
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wo FIG. 175.—Organisation of Myzostorua cirriferum, after v. Graft. To the left the parapodia(p), the suckers (sn), and the male genital apparatus are represented. To the right the entericbranches (</«) and ovaries (o). c, Cirri; php, pharyngeal tentacles ; ph, pharynx; pht, pharyngealpouch ; ill, stomach (mid-gut); ed, hind-gut; «, uterus ; ivo, female genital aperture, which entersthe cloaca; Mo, aperture of cloaca; pm, muscles for moving the parapodia; mo, male genitalaperture ; s6, sperm vesicle; vd, vas deferens ; li, testes ; p, parapodia with hooks and supportingrod. the Platodes, It is, however, probable that this is more a caseof analogy than of homology. In the sexually mature animalsthe parenchyma is filled with numerous egg cells which lie in VERMES—GENITAL OR( L 1 .V,S 263 masses between the branches of the intestine, especially on the dorsalside. These masses of eggs are regarded as ovaries. It is, however,possible that they consist of eggs which have left the r

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