No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 407 



this form. Only two individuals of Carinella were examined 

 (both from Bergen, Norway) ; in the one all the gregarines were 

 large, in the other of a smaller size.) 



The hucleoli are nearly always more numerous than in the 

 preceding species of gregarine, the number varying from four to 

 about twenty-six, in those stages found (Figs. 22-35). I^i the 

 larger nuclei they are usually more numerous than in the smaller 

 ones, but exceptions to this rule are quite frequent. In the 

 same nucleus some are nearly or quite spherical, others very 

 irregularly lobular in outline. Their size within a given nucleus 

 is also very variable, though as a rule they are unequal in their 

 dimensions. In the larger nuclei the nucleoli are larger (or at 

 least some of them are) than in the smaller nuclei. In a given 

 nucleus there may be either (i) from two to four larger nucleoli 

 and a number of smaller ones ; or (2) a single large nucleolus 

 and several much smaller ones. In the smaller nuclei the 

 nucleoli are more equal in size than in the larger ones. The 

 largest nucleoli in a nucleus are as a rule of oval or spherical 

 form, with regular contour (an exception is seen in Fig. 26) ; 

 the irregularly lobular nucleoli (Figs. 23, 25, 27, 28, 33) are 

 usually of medium or small size. There is no apparent regu- 

 larity with regard to their distribution in the nucleus. None of 

 the' nucleoli appear to have limiting membranes. 



All these gregarines were fixed with alcoholic solution of 

 corrosive sublimate. With the double stain, haematoxylin and 

 eosin, the larger nucleoli were stained with a deep blackish 

 red, the smaller ones either of the same color or a clearer red ; 

 all became stained so intensely by this method that the vacu- 

 oles in them were greatly obscured (Figs. 27 and 28). 



The Ehrlich-Biondi method produces a yellowish brown or 

 reddish stain of the nucleoli, differences of stain being observ- 

 able in the different nucleoli of the same nucleus (Figs. 26, 

 31-35). This staining method brings out very clearly the 

 vacuoles in the homogeneous (.-*) ground substance of the 

 nucleolus ; the structureless substance of these vacuoles 

 stains less intensely than the enveloping substance. Vacu- 

 oles are absent in the smallest nucleoli, as well as in those of 

 irregular form ; in the larger ones they are almost invariably 



