ELECTRON MICROSCOPE STUDY OF T H E VITELLINE BODY OF SOME SPIDER OOCYTES BY J. ROBERTO $OTELO AXeD

The vitelline body in spider oocytes was first seen by von Wittich (1845, cited by Bounoure (2)) and shortly afterwards by yon Siebold (1848). I t was described as a round body located near the nucleus. Balbiani some years later (1) proposed that a relationship exists between the vitellus formation and the developmental changes taking place in this body during the oocyte growth. In regard to its morphological constitution he advanced the hypothesis that it is formed by a condensation of material around the cell center. I t is generally admitted, according to Balbiani's concept, that vitellus (or yolk) formation is related in some way to the viteIline body, but little agreement can be found in the several descriptions concerning the morphology of the body itself. The early accounts of the vitelline body describe it as consisting of a more or less thick layer of multiple, concentrically arranged lamellae surrounding a central core composed of granular or vesicular elements. I t was also claimed that round or crescentic masses of granular or filamentous material, located near the oocyte nucleus, were vitelline bodies. Such variations were noted in different vertebrate as well as invertebrate oocytes (see Prenant (16), Wilson (27)). Histochemical studies (25) made more recently have demonstrated the existence of ribonucleic acid in the vitelline body of some animal species. Also, polarized light studies have shown (12) that the lamellar layer has negative birefringence, and this optical behavior has been attributed to the mitochondria. Notice must be taken of the fact that mitochondria were considered the main constituent of the lamellae. The structure of the central core was not clearly defined, except for the probable presence of the cell center. Even though vitelline bodies are especially characteristic of oocytes, other paranuclear bodies existing in somatic or germinal cells have often been described as similar to them.