738 LIFE HISTORIES OF THE PROTOZOA. 
olus, presenting some seconds later a great number of little 
refracting corpuscles, of very variable dimensions, which are also 
nucleoli. Some of these enlarge considerably, whilst the primi- 
tive nucleolus diminishes in volume little by little, finally disap- 
pearing. The number of nucleoli varies at every instant.” These 
novel observations are considered of great importance by Van 
Beneden as showing that the nucleolus of the Gregarina, and con- 
sequently the nucleoli of cells generally are sometimes, if not 
always, devoid of a membrane. And he draws the. inference 
“that the nucleus of a cell is not necessarily a vesicle, and that 
Development of Gregarina. 
contrary to the generally received opinion, a nucleus of a cell may 
be equally devoid of membrane,” though we may add tl oe 
it in the Gregarina of the lobster. Van Beneden distinguishes 
three kinds of motions in the Gregarine. 1. They present a Lies 
slow movement of translation, in a straight line and without bed 
possibility of distinguishing any contraction of the walls ol ae 
body which could be considered as the cause of the movement. 
It seems impossible to account for this kind of motion. 2 
next kind of movement consists in the lateral displacemen? yi 
every part, taking place suddenly and often very violently, from * 
yat he saw 
