298 MONTGOMERY. [\'ol. XV. 



Bander auszumachen, sondern nur einen Bestandtheil derselben 

 zu bilden, der bei mangelhafter Ernahrung der Gewebe zuerst 

 schwindet." 



Lang ('84) remarks of the egg cells of Polyclad Ttirbellaria: 

 " Das Kernkorperchen oder der Keimfleck ist stets als ein 

 kugliger, relativ sehr grosser, intensiv gefarbter Kbrper zu 

 unterscheiden." 



Vejdovsky ('84) noticed a single nucleolus in the eggs of 

 Oligochacta. 



Wielowiejski ('84) studied the egg cells of various Arthropoda. 

 In the Araneina and Acarina the larger nucleolus contains a 

 single large or several smaller vacuoles, though no pulsating 

 or amoeboid movements were noticed (in opposition to the 

 observations of Balbiani). In Drassns and Lycosa there is a 

 small mass of granules in place of a germinal spot ; in Oniscus, 

 a single large nucleolus; in Astaais, numerous peripheral ones; 

 and in Musca, a large, irregularly spherical one. (He notes 

 that the germinal vesicle differs from all other nuclei in that 

 its contents do not stain at all, or only faintly, with acetic acid 

 methylen-green solution.) 



Will ('84) studied in life the eggs of Bufo and Rana. Larger 

 and smaller nucleoli may be distinguished; the latter increase 

 somewhat in size, but never attain the dimensions of the 

 preceding. Those nucleoli, then, which lie close to the nuclear 

 membrane cause small protuberances (" Knospen ") of this 

 membrane, each such bud ne.xt breaks off from the nucleus, and, 

 still enclosing a nucleolus within itself, wanders towards the 

 periphery of the cell, and there becomes a " Dotterkern," the 

 disintegration of which furnishes the yolk granules. 



1883. 



Van Bambeke ('85) reviews the opinions of the following 

 writers in regard to the nature of nucleoli: Flemming ('82), 

 Strasburger, Pfitzner ('81), Retzius ('81), Leydig ('83), Balbiani 

 (■81), Korschelt ('84), R. Hertwig ("84), Van Beneden ('83), 

 Frommann ('84), Carnoy ('84), Brass, Wielowiejski ('84), and 

 Rabl ('84). Nucleoli are rarely absent, and hence they must 

 be regarded as an essential element of the nucleus. "Le 



