Ueber doe Anwendung des Capillarelektrometers für das Studium der Muskulären Einzelschwankung / von Prof. Burdon Sanderson.

  • Sanderson, Burdon.
Date:
[1898]
Catalogue details

Licence: Public Domain Mark

Credit: Ueber doe Anwendung des Capillarelektrometers für das Studium der Muskulären Einzelschwankung / von Prof. Burdon Sanderson. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    The morphology of the nephridial funnels is further complicated by the fact that from the condition where some of the nephrostomes function for discharge both of gonocytes and ek-phorocytes (a stage represented in ontogeny of Amphioxus by the period where the peri- gonadial coelom communicated freely with the pronephric funnel, and its mesonephric homologue in Scyllium [Boveri]) to that in which some funnels function solely for the exit of gonocytes whilst others having lost their egestive function atrophy, the tubules only remaining. In the development of any pronephric (or for that matter meso- nephric) tubule the funnel and tubule are first formed before the cells lining the walls take on an excretory function or become closely connected by glomeruli to the vascular System, so that it is not unrea- sonable to assume that the excretory function of the tubules has been secondarily acquired and that the pronephros therefore first functioned for the egestion of ek-phorocytes and gonocytes and that later the excretory function was added to it. (see below.) Upon the evolution of the mesonephros followed by the meta- nephros each of these Organs in turn was better adapted than its pre- decessor for excretory functions mainly from the fact that each was nearer the point of exit to the exterior than the one before it. This factor, however, has no bearing upon the gonocytic and egestive function and hence the primitive pronephric funnel persists for the re-productive function (Mullerian funnel)42. If we suppose the primitive Chordate hermaphrodite ancestor to have been protandrous43 then one would expect the male gonocytes, ripening first, to be discharged by the mesonephric funnels, which are nearer to the exterior and the female toretain their original pronephric connection. Theseparation betweenthe Wolffian and Mullerian ducts may then be an expression of the Separation between the ducts of the two sexes in one individual rather than between the excretory and sexual functions. 3) The Polyzoa. The absence of any definite nephridia in the marine colonial Polyzoa is a well-known morphological fact44. This segmented and drain the primary body-cavity. Compare: Gegenbaur, Comp. Anat. and R. S. Bergh, Kosmos. 1885. 42 F. M. Balfour, Journ. Anat. and Physiol. X. 1875. 43 G. B. Howes, Linn.Soc. Journ. Vol.XXIII. p. 544. — A. T. Masterman, Scottish Fish. Board Rep. 1895. 44 In Loxosoma and Pedicellina have been described tubulär excretory Organs with blind flame-cell terminations.[Harmer, Joliet.) »It is probable that the flame cell termination, situated in the ,primary“ ,body-cavity“, is morphologically different
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