54 



Avhicli the one, very small, occupies the cavity of the anterior 

 globular enlargement, and the other fills all the rest of the 

 body of the animal. The whole cavity of the body of the 

 Gregarina is filled with a granular matter, formed by a viscid 

 liquid which is perfectly transparent. This holds in suspen- 

 sion fine granulations of a rounded form, which are formed 

 by a highly refractive and sHghtly yellow matter. The 

 quantity of granules with which the liquid matrix is charged 

 increases with the size of the Gregarinse, and, moreover, the 

 opacity of the animal is greater in proportion as its dimen- 

 sions are larger. This granular liquid which occupies all the 

 cavity of the cell is very mobile, and may be seen shifting 

 about in the interior of the membrane whilst the animal 

 executes its movements. 



It is always easy to distinguish the nucleus of the cell in 

 suspension in the granular liquid which occupies all its 

 cavity. It has, normally, a regular ellijjsoid form, and its 

 dimensions vary with those of the Gregarina. In the largest 

 individuals which I have found it measured '13 of a milli- 

 metre across its major axis, '08 to '10 of a millimetre across 

 its minor axis. This nucleus presents a membrane which is 

 perfectly distinguishable, and the cavity of the vesicle is filled 

 by a homogeneous, colourless, and transparent liquid. This 

 nucleus is not a solid body destitute of a membrane, as M. 

 von Frantzius thought it. It is easy to assure oneself of this 

 by isolating the nvicleus, and subjecting it to pressure. One 

 may then see, at a given moment, a bursting of the membrane 

 take place, and the liquid contents of the nucleus escape by 

 the aperture produced. The membrane of the nucleus is, 

 hoAvever, very thin, and it is this which explains the modi- 

 fications of form which the vesicle undergoes when external 

 pressure is brought to bear on it. I have seen a nucleus 

 affect successively the forms represented in fig. 6, a, h, c, d, 

 in a Gregarina which glided on the glass slip placed on the 

 microscope-stage, picking its way among the various solid 

 contents of the intestine of a lobster ; but the form of the 

 nucleus never changed itself spontaneously, and apart from 

 the infiuence of external causes. 



The most important fact of all that are put out in this 

 notice concerns the spontaneous apparition and the disappear- 

 ance of the nucleoli of the nucleus in a very short space of 

 time. If one of these Gregarinse of moderate size is ob- 

 served, the nucleus is seen at first provided with a single 

 nucleolus, presenting, some seconds later, a great number of 

 little refracting corpuscles, of very variable dimensions, Avhich 

 are also nucleoli. Some of these enlarge considerably, whilst 



