Title: The Biological bulletin
Identifier: biologicalbullet159mari (find matches)
Year: [1] (s)
Authors: Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983
Subjects: Biology; Zoology; Biology; Marine Biology
Publisher: Woods Hole, Mass. : Marine Biological Laboratory
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
SYMPLEGMA GANGLIA AND REPRODUCTION 225
Text Appearing After Image:
FIGURE 5. Secondary lysosomes appearing in the neurosecretory cells of 10-day-old soli- tary zooids after isolation. Lys = secondary lysosome. A neurohemal region where neurosecretory materials are released into the cir- culatory system could not be identified in the present study. Axonal endings of neurosecretory cells may exist near the ganglion, since axons containing the neurosecretory granules were found only near the ganglion. A well-defined neuro- hemal organ such as the median eminence of vertebrates, the sinus gland of crusta- ceans, and the corpus cardiacum of insects was not found in Symplcgma. Such dif- fuse and short-range distribution of the axon terminals is known in the ganglia of molluscs (Frazier ct a/., 1967; Toevs and Brackenburry, 1969; Loh ct a!., 1973). Many studies concerning the mechanism of reproduction in ascidians have been carried out since Julin (1881) postulated a homology of the neural gland with the hypophysis of vertebrates. Previous studies examining possible gonadotropic potency of the neural complex showed contradictory results: Butcher, 1930; Hogg, 1937; and Carlisle, 1951, concluded that there was a positive function but Dodd, 1955, and Sawyer, 1959, showed negative function. However, the bioassay system of earlier investigators, using tissues of vertebrates, has to be reconsidered because there is no reason to suppose that similar phenomena in such phylogenetically distinct organisms are regulated by the same materials. For example, gonadotropin and progesterone affect oocyte maturation in vertebrates, but the same phenomenon in starfish is regulated by a peptide hormone from the nervous system and 1-methyladenine (see Kanatani, 1973, for review). Therefore, in examining hor- monal activity of a species, animals of at the very least the same phylum must be used in order for bioassays to have relevance. Many studies concerning the function of neurosecretory cells on gonad develop- ment indicate that distinctly contrasting control mechanisms operate in various

Note About Images