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 (vīt′l-âr′ē-əm, vĭt′-)
n. pl. vi·tel·lar·i·ums or vi·tel·lar·i·a (-ē-ə)
A group of glands in flatworms and certain other invertebrates that secrete yolk.

[New Latin, from Latin vitellus, egg yolk; see vitellus.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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Nulliparous stages were classified as: nulliparous 1 (where the germarium and vitellarium are not differentiated and are without follicles); nulliparous 2 (well-defined ovarioles with multiple follicles, the proximal follicle transparent indicating that it had not completed maturation); and nulliparous 3 (proximal follicle more opaque [mature] and close to ovulation).
Egg development occurred anteriorly to posteriorly along the ovariole, with two distinctly recognizable regions: the germarium and the vitellarium. The germarium contained a number of spherical cells observed as either free or clustered (Figure 4(a)).
In the necrotic mass, the only recognizable features were the ova and the vitellarium, which atrophied and resulted in tyrosine-positive staining within the mass.
Uterus extending anteriorly on left side; uterine sac median, without lateral sacculations in posterior half of body, well separated from acetabulum, receiving uterus near middle; vitellarium undeveloped; no eggs (Fig.
Dissection of the females during this period confirmed that the ovariole was immature and the vitellarium had no developed oocytes or that the development of the latter was only incipient.
In polytrophic meroistic ovaries, such as the ovary of bees, each ovarian follicle is constituted by one or several nurse cells that accompany the oocytes in the vitellarium. Usually the follicles become divided into oocytic and nurse chambers, both surrounded by a layer of follicular cells.
Diet C: Once the vitellarium sac had been absorbed, rotifers, Brachionus plicatilis, were given at a rate of 10/mL for 10 days; thereafter, 2 cladocerans D.
To study the chick embryo, Fabrici, 1942b, 141-48, begins with basically seven structures, though the uterus signified three of them: the uterus, the egg, the vitellarium (group of yolks) or raceme (ovary, group of eggs), the pediolus (stalk to which yolks are attached), the peduncle (attaching yolk to the stalk), the infundibilum (the passage between the first and second uterus), and the podex (where the second uterus terminates).
Generally only the terminal follicle within an ovariole is vitellogenic, there being a distinct demarcation between the previtellarium and the vitellarium of the ovariole.
The ovarioles were of the telotrophic meroistic type, wherein nurse cells in the distal germarium provide nutrients to developing follicles contained in the vitellarium (Chapman 1998).