No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 333 



Bohmig ('93), Rhodope veranii : the single nucleolus in older 

 eggs contains one or several vacuoles. 



Brauer ('93) investigated the spermatogenesis of Ascaris 

 megalocephala : there is one homogeneous nucleolus in the 

 spermatogonium, which becomes smaller in the spermatocyte 

 and often evinces a large vacuole. The nucleolus is smaller 

 than the centrosome (which is at this stage enclosed in the 

 nucleus), and stains differently from the latter. 



Brooks ('93), Salpa : the single large nucleolus of the ovarian 

 ovum " is suspended near the center of the nucleus by a net- 

 work of fine threads." 



Fick ('93) studied the maturation of the ^%g of the Axolotl. 

 In the germinal vesicle lies a group of nucleoli, which vary in 

 size from 3/a to i6/i ; some contain a single vacuole, and some 

 stain more deeply than others. The greater number of them 

 disappear at the time of the longitudinal division of the chro- 

 mosomes, though a few may remain in the yolk for a certain 

 time. " Bei den Nucleolen des Keimblaschens liegt es sehr 

 nahe mit Strasburger und Pfitzner daran zu denken, dass sie 

 vielleicht eine Art Reservestoffbehalter darstellen " ; further, 

 he holds that the nucleoli " in einer allerdings noch nicht auf- 

 geklarten Beziehung zu den Veranderungen des Chromatins 

 stehen, da sie bei der Ausbildung der Chromosomen fiir die 

 erste Spindel vollstandig verschwinden." 



Frenzel ('93a) studied the nucleoli of various Gregarines. 

 In Gregarina statirae the single nucleolus, which he terms 

 " Morulit," appears " eigenthiimlich glanzend mit einem 

 schwach gelblichen Schimmer und dabei an der Oberflache 

 rauh und warzig-runzelig. ... In seinen Reaktionen verhalt 

 er sich an alien Orten ahnlich wie Nuklein." In G. bers^i a 

 single Morulit is present. In the embryo of Pyxinia crystalligera 

 there is a single Morulit ; in older individuals the nucleus 

 "enthalt mehrere helle, klare, glattrandige und lebhaft glan- 

 zende Nucleoli . . . die oft noch einen Fliissigkeitsraum im 

 Innern bergen." In Gregarina poj'tuni, Callytitrochlamys, and 

 Aggregata portmiidanim there are several nucleoli in the nucleus. 



Frenzel ('93b) hepatopancreas cells of Astacus: in the fat 

 and ferment cells a single nucleolus is present ; in the amitosis 



