278 Illinois State Laboratory of Natural History. 



shrunken and irregular. In the larger number of instances 

 of this stage under observation the cells appeared normal, 

 showing no trace of degeneration or division. In one instance 

 only have I found a specimen in which the vegetative cells 

 had divided beyond question. This was a colony in which 

 the gonidia had completed their division but had not escaped. 

 Three of the vegetative cells were in the two-cell stage and one 

 was undivided. In two instances matured colonies have been 

 found in which four smaller daughter colonies (of eight and 

 sixteen cells respectively) were present at one pole. 



The gonidial cells (PL XXXVI. , Fig. 3) constitute the 

 remainder of the colony. They usually number 28, rarely 

 12 or 60, and occupy the parts behind the anterior polar 

 circle of vegetative cells. These cells in most instances can 

 be easily distinguished by their larger size. In form they are 

 spherical, though some specimens in preserved material are 

 slightly flattened on their inner ends. In diameter they range 

 in seemingly full-grown colonies from 15 to 25 yu, averaging 

 in twelve specimens 1 9.2 yu. Their dimensions just before their 

 division, that is in colonies in which division has begun, also 

 show the extreme range quoted above, the smaller diameter 

 having been found in a sixteen-cell colony. As a rule the 

 gonidia are all of the same size, but occasionally specimens 

 have been found in which one or more dwarf cells occur 

 among them. These are irregular in their distribution and 

 can be distinguished at once from the vegetative cells by 

 their position. Similar dwarf cells were found in both Pan- 

 dorina and Eudorina. In matured colonies gonidial cells are 

 frequently found which fail to divide. The gonidia are of a 

 light green color, a trifle darker than the vegetative cells. 

 Their color in general is similar to that in Eudorina, and is 

 sonnwhat lighter than that in Yolvox and Pandorina, with 

 which they are associated. 



A distinct cell membrane (c. m.) is found about each of the 

 cells. In the living condition and in the material preserved 

 in formalin it forms a highly refractive hyaline layer, about 

 1 // in thickness, outside of the green contents of the cell. It 

 stains very faintly in hematoxylin and assumes a deep brown 



