No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 509 



gory should not be classed small masses of nucleolar substance 

 grouped around a larger one, these being normal phenomena 

 during the growth period of nucleoli. 



Reticulations within the nucleolar substance have been de- 

 scribed by some few authors. Thus Carnoy ('85, '97a), Meunier 

 ('86), and Moll ('93) described nucleoli containing a skein of 

 chromatin, but Zacharias and Strasburger ('88) did not find 

 anything resembling these supposed skeins described for 

 Spirogyra. Leydig ('88) states that the germinal spot of Lycosa 

 " bietet das Bild eines Knauels dar." Fromann ('84) described 

 the nucleolar substance as consisting of granules connected by 

 fibers, Biitschli ('80) found the nucleoli of Dinojlagellata to 

 contain a fine reticulum, and Davidoff ('89) states that the 

 germinal spot of Distaplia takes up portions of the nuclear 

 reticulum into itself (but cf. Bancroft, '98, and Shafer, '80). The 

 only structure which was found by me to resemble a skein was 

 present in the later stages of the germinal spot of Polydora ; 

 but in this object, owing to the gradual confluence of the vacu- 

 oles, which thus produce anastomosing channels of vacuolar 

 substance in the ground substance of the nucleolus, it is the 

 true ground substance which represents a skein-like appear- 

 ance. It is very probable that Carnoy and his followers have 

 mistaken the vacuolar substance for the ground substance, and 

 have considered the true ground substance to be chromatin ; 

 I am forced to conclude that in all probability there are no 

 skeins of chromatin lying in any metazoan nucleolus, since I 

 have never found any evidence of chromatin in it in any meta- 

 zoan cell. But it is not improbable that in the nuclei of 

 gregarines chromatin may be massed in some or all of the 

 nucleoli. 



Nucleolini, granules within the nucleolus, have frequently 

 been observed. A single nucleolinus to a nucleolus has been 

 described by Vejdovsky ('95b), Morgan ('96), Agassiz ('57), 

 Kleinenberg ('72), Leydig ('88), Macfarlane ('85), Lavdowsky 

 ('98), A. Brandt ('78), Van Bambeke ('86), Kosinski ('87, '93) ; 

 several nucleolini to a nucleolus, by Burger ('90), Rhumbler 

 ('93), Holl ('93), Wolters ('9l), Schron ('65), Scharff ('88), See- 

 liger ('82), Gjurasin (-93), Haeckel ('74), Mann (-92), Van Bam- 



