No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 
339 
newt. He thinks “that certain deutogenic substances are 
formed in the [germinal] vesicle, perhaps through the agency 
of the nucleoli, and are then sent forth to share in the building 
up of the cell,” i.e., of the yolk particles. “The nucleoli in 
the young egg appear arranged along the chromatin threads, 
and possibly originate from the thread substance.” Later they 
lose this connection, grow larger, and assume a peripheral 
position within the nucleus. There is apparently no division 
of the nucleoli; they “ attain their maximum size shortly 
before their centripetal movement.” Having arrived at the 
periphery of the nucleus, the nucleoli commence to stain less 
deeply, their contours become uneven, and they then wander 
back to the center of the nucleus, where they disintegrate. 
He does not agree with O. Schultze (’87) that the nucleolar 
particles build up the chromosomes. 
Kaiser (’93) found in the egg of Echinorhynchus bipennis one 
large, spherical, peripherally situated nucleolus. It disappears 
before the pole spindle is produced. 
Lustig and Galeotti (’93), mentioned by Lardowsky (’94), con¬ 
sider that the centrosome does not proceed from the nucleolus. 
Mertens (’93), ovum of Homo: two or three nucleoli are present, 
consisting of a central clearer and a peripheral darker portion; 
it is probable that several smaller ones may fuse together to 
form a larger one ; they are at first in intimate connection with 
the chromatin filaments, but later lose this connection and gradu¬ 
ally cease to stain with safranin. The Balbianian corpuscle 
is an extruded nucleolus : “c’est alors aussi que nous nous 
^tondrons quelque peu sur l’expulsion des parties chromatiques 
du noyaux, expulsion qui parait affecter les memes charact&res 
chez les oiseaux et les mammiferes ”; eliminated nucleoli 
(“ grains chromatiques ”) as well as attraction spheres have been 
described as Balbianian corpuscles. Ovum of Pica: in young 
ovules there is one nucleolus which arises as follows : at one 
point in the nucleus the reticulum concentrates itself, and 
here a certain number of the filaments fuse together, thus 
producing the nucleolus. The chromatin is at first irregularly 
arranged in the nucleolus, but “ finit par etre egalement dense 
dans toutes les parties de la tache germinative,” and subse- 
