The firm membrane enclosing the ripe deposited ovum of Myxine is a primary egg membrane produced within the follicle.
The polar threads are processes from this membrane.
The membrane is single and not differentiated into layers: it possesses minute pores perpendicular to its surface, and is therefore a zona radiata.
The zona radiata in Myxine is homologous with the single or double zona radiata of Teleosteans and of Petromyzon.
The membrane at one pole of the ovum, that at which the protoplasmic germinal disc is situated, is perforated by a micropyle.
The micropyle is produced by a process from the follicular epithelium.
The immature testis in Myxine consists of a thickened border of the mesorchium containing more or less spherical capsules, which are filled with hyaline nucleated spermatoblasts.
A large proportion of immature Myxine are hermaphrodite, the posterior portion of the reproductive organ containing testicular capsules which have the same structure as those found in the male.
Spermatozoa have been found in the testicular portion of the hermaphrodite organ, but not in the males.