File:Text-book of comparative anatomy (1898) (14592367747).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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nto groups (plates) of 32-64spermoid gametes, each of which has two flagella. The plates severthemselves and swim about freely. If such a structure comes in PROTOZOA 21 contact with a female colony, it remains attached to it and breaks upinto single male gametes. Volvo? (which leads almost directly by itsmethod of reproduction to the higher plants and animals) is closelyconnected with Endorina. In Volvox (Fig. 21) the colony appears on a higher scale of de-velopment, as a division of labour takes place among the differentindividuals. Only some individuals are capable of reproduction ; in theasexual generation these individuals are the parthenogonidia (everyparthenogonidium produces, by continuous incomplete fission, a colonywhich separates from the mother colony); in the sexual generationthey are gametes. Unlike the Endorina, Volwx produces, in one andthe same colony, male and female gametes. The female gametes aresimple individuals of the colony, only distinguished by their greater o
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0.- S V -s FIG. 21.—Volvox globator.—Sexual, hermaphrodite colony, after Cienkovsky and Butschli,combined and somewhat diagrammatic. .S, Male gametes (spermatozoa); 0, female gametes (eggs). growth. The male gametes, on the contrary, arise in masses, by thesuccessive fission of certain individuals (cells) of the colony. From onesuch mother-cell as many as 128 male gametes may proceed. Themale gametes separate, move about by means of their flagella, andcopulate with the female gametes. By successive division (into 2, 4,8, 16, and so on) of the stationary zygotes a colony, i.e. a young Volco.i;arises. We have here before us a true alternation of generations,asexually reproducing generations alternating with sexually reproducinggenerations. The sexual reproduction corresponds with the method ofreproduction of the Metazoa and higher plants. The hermaphroditeVolvox (Flagellate colony) corresponds with a very simple hermaphro-dite metazoon. The female gametes represent the eggs, the mal

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