No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 361 
Waldeyer (’95), cited by Flemming (’96), regards the nucleoli 
as morphologically distinct from the chromatin reticulum. 
Wheeler (’95) observed in Myzostoma glabrum that the 
nucleolus is large and vacuolated, and after the reduction 
mitosis, “ remains in the cytoplasm as an inert mass, gradually 
melting away, but not disappearing until about the eight-cell 
stage, when it may often be found in the largest blasto- 
mere.” 
Wilcox (’95) holds that in the spermatocytes of Cicada the 
nucleoli stand in genetic connection with the centrosomes, 
and adds, “ It is probable that different structures have been 
called nucleoli by different authors.” 
i 8 g 6 . 
Auerbach (’96) studied the spermatogenesis of Paludina: 
the nucleus of the spermatogonium contains a number of 
large, more or less spherical bodies (“ Karyosomen ”); each 
nucleolus (of the resting spermatogonium), after simultaneous 
staining with acid fuchsine and methylen green, shows a 
central red portion and a blue peripheral shell. “ Es besteht 
also eine Zeit lang der Nucleolus aus einer erythrophilen Cen- 
tralmasse und einer kyanophilen Rinde.” In the subsequent 
nuclear division of these cells the nucleoli disappear. “ Fest 
steht nur, dass in dem Netzstadium die Nucleoli als solche 
verschwinden, und dass ihre Rindensubstanz auf die angegebene 
Art zu einem Teile des intranuklearen Netzwerkes wird, der 
anfangs noch unterscheidbar ist, dann aber durch Auseinander- 
riicken der Knotenpunkte sich in dem ubrigen Fadennetze ver- 
liert.” In the spirem stage there are one or two small, spherical, 
red-staining bodies in the nucleus ; he was unable to determine 
whether these stand in any genetic relation to the nucleoli, 
which had previously vanished. In the spermioblast (which 
changes directly into the hair-shaped spermatozoon) a small, 
red-staining body lies within the nucleus, but subsequently 
disappears ; Auerbach supposes that it wanders out of the 
nucleus and fuses with the “ Nebenkern.” 
Doflein (’96), maturation of the egg of Tubularia larynx: 
the single large nucleolus is suspended by achromatic fibers in 
