File:Text-book of comparative anatomy (1898) (14779002242).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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ture animals they are retained at the best as rudiments. Thesperm formative cells are early gathered into special sperm sacs, inwhich they develop further and produce the ripe spermatozoa. Thesesperm sacs, formerly regarded as testes, are large vesicles whichdevelop on the dissepiments of the testicle segments as sac-like 260 COMPARATIVE ANATOMY CHAP. outgrowths of their posterior lamella?. They are divided internallyby lamella? into numerous compartments and chambers, in whichthe developing spermatozoa lie, and are in open communicationwith the body cavity. The manner in Avhich the sperm formativecells pass out of the testes into the sperm sacs is not known.The sperm sacs, even in nearly related genera and species, differconsiderably in their number and special arrangement. In someLumbricidce a middle unpaired portion is formed, a sperm capsule, andthe sperm sacs then appear merely as paired appendages to thiscapsule. In the Chcetogastridce alone no sperm sacs are developed. for bl 4
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\ \ \ b?rL> dfy to FIG. 174.—Lumbricus agricola. Genital organs, after Vogt and Yung. To the right thesperm sacs and a part of the unpaired sperm capsule are removed. 6m, Ventral chord ; sfj, sU,receptacula seminis ; ?j, U, sperm funnels ; s&», unpaired sperm capsule; di, dissepiments cut offat their bases ; vd, vas deferens; fo, funnels of the oviducts ; o, ovaries ; ov, oviduct; di\, part ofthe dissepiment between the 13th and 14th segments; sfy, sb*, sb3, paired sperm sacs; Tij, 7io,testes ; VIII-XV, Sth to 15th segments. The sperm formative cells in this family develop fully in the bodycavity, and the ripe spermatozoa are collected direct out of the coelomicfluid by the funnels of the sperm ducts. Each sperm duet consistsof a preseptal funnel, and of a duct which penetrates the septumand opens externally through a widened terminal division, theatrium (arising by an invagination of the outer integument). Whereonly one pair of testes is present there is generally only one

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