Oocytes of 9 bird species were examined, light microscopy, cytochemistry and auto-radiography being employed.
The absence of nucleoli in the oocytes of adult females appeared to be characteristic pattern of bird oogenesis. In all the species studied,
except Gallus domesticus, nucleolus-like structures develope on the lampbrush chromosomes. However, these formations do not contain
RNA. Neither RNA, nor protein synthesis was revealed by autoradiography, general proteins were discovered in these only cytoche-mically.
The structures may be considered as nuclear protein bodies widely distributed in the oocytes of various animals whose functional role still remains obscure.
The protein bodies in bird oocytes are always associated with chromosomes. They appear at the beginning of chromosome despiralization and increase in size till the formation of lateral loops is completed. The maximal measurements of the protein bodies reach in different species from 5 to 15 ^ depending on their number per oocyte nucleus, and on the number of chromosomes with which either forming protein body is connected.
In all the species examined, except Gallus domesticus, the karyosphere formation occurs at the initial steps of vitellogenesis, the essential role belonging to the protein bodies. The origin and possible function of the protein bodies in the bird oocyte nuclei are discussed.