No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 
337 
von dem Kernplasma langsam zu trennen beginnt.” He could 
not exactly determine how long the nucleolus remains in the egg 
after that, but considers the fact important, “ dass der Haupt- 
nucleolus zur Zeit der Umbildung der Keimblaschensubstanz 
ohne bemerkbare Volumverminderung fort besteht ”; it is at 
this time (after the disappearance of the nuclear membrane), 
to use his terminology, a “ Metanucleolus.” 
Henneguy (’93) studied principally the genesis and occur¬ 
rence of the yolk nuclei, “corps vitellin de Balbiani,” in the 
ovarian egg of various vertebrates. This body is absent in the 
ova of the Rabbity Bitchy Mole y RhinolophiiSy Cow f Antelope , 
Baboon; and in Lizards , Galeus y Raja, and ScyIlium. In the 
rat it consists of a peripheral clearer portion and a central 
denser core ; it stains with eosin, safranin, and haematoxylin, 
but not with methyl green or gentian violet. In the bat it 
encloses a spherical corpuscle. It is also present in the chicken. 
Though absent in Bnfo and Triton y it is found in Rana tempo- 
rariay where it is much the same as in birds, enclosing a more 
deeply staining portion. In the trout the corpuscle of Balbiani is 
as in the rat, but larger (twenty). Sygnathus: the very young 
egg contains a nucleus “ renfermant un r6seau chromatique bien 
developpe ” (his Fig. 20 would show three small nucleoli enclosed 
in this “ reseau ”); in older eggs the nuclear membrane is lined 
by a large number of nucleoli, and “ le centre du noyau est 
occupe par une petite masse finement granuleuse et teintee en 
rose par la safranine, tandisque le reste du contenu demeure 
incolore. Le protoplasma ovulaire est dgalement faiblement 
colore et renferme un corpuscule arrondi, refringent comme les 
taches germinatives et retenant la safranine avec la meme 
intensite que ces derni&res ” ; this corpuscle at the time of its 
first appearance is flattened against the outer surface of 
the nuclear membrane. Subsequently this intravitelline body 
becomes elliptical in form, with its long axis parallel to the surface 
of the egg : “ il est de plus au contact immddiat par son bord 
externe avec une amas arrondi, constitue par une substance 
fondamentale d’apparence homogene, mais remplie de granula¬ 
tions tres colordes. A un stade plus avancd tout le corps 
refringent s’est transforme en un amas let qu’on Tobserve dans 
