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 Mysostoma glabruni that the 

 nucleolus is large and vacuolated, and after the reduction 

 mitosis, " remains in the cytoplasm as an inert mass, gradually 

 melting away, but nox 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." 



i8g6. 



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 Telle des intranuklearen Netzwerkes wird, der 

 anfangs noch unterscheidbar ist, dann aber durch Auseinander- 

 riicken der Knotenpunkte sich in dem tibrigen 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." 



Doilein ('96), maturation of the egg of Tubiilaria larynx : 

 the single large nucleolus is suspended by achromatic fibers in 



