Archive image from page 122 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana05todd Year: 1859 Structure and Formation of Ova in Acephala. (.From Lecaze Duthiers.') a. Portion of the ovary with three pediculated ovicapsules and contained ova from Cardium rusti- curn, magnified 400 diameters; the micropyle is afterwards formed at the place where the pe'dicles are detached from the secreting coaca of the ovary. b. Unripe ovum of Spondylus gtederopus magni- fied 170 diameters, showing the remains of the cap- sule at the upper part, and the projection of t
Archive image from page 122 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana05todd Year: 1859 Structure and Formation of Ova in Acephala. (.From Lecaze Duthiers.') a. Portion of the ovary with three pediculated ovicapsules and contained ova from Cardium rusti- curn, magnified 400 diameters; the micropyle is afterwards formed at the place where the pe'dicles are detached from the secreting coaca of the ovary. b. Unripe ovum of Spondylus gtederopus magni- fied 170 diameters, showing the remains of the cap- sule at the upper part, and the projection of the vitelline membrane at the same place where the micropyle is situated. c. Kipe ovum of the same burst by pressure, showing the escape of some yolk granules through the micropyle and into the space between the yolk and the outer membrane. Iii'this and the previous figure the double state of the macula is represented. shown that the micropyle of the Acephalous Mollusca owes its origin to the early pediculated attachment of the ovum. This has been fully brought out by the observations of Hesslin'g in Unio and Anodonta, of Leydig in Venus, and of Lecaze Duthiers in Cardium and some other genera. From these observations it appears that the ova first arise in the ova- rian stroma by the formation of the ger- minal vesicles, as in most other animals, eacli vesicle possessing a distinct single macula. These vesicles come very soon to be surrounded by some of the primitive or finely granu- lar yolk, which gradually increases in quantity. These parts are from a very early period en- closed by a membrane which may be regarded as vitelline, but which is differently disposed from that in any of the animals previously re- ferred to ; for, instead of having a regular and complete spheroidal or vesicular form, this membrane is elongated at one part into a pedicle, so as to give the whole of the early ova a pyriform shape, and so as to attach them to the ovarian substance by the pediculated
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