of the Trichodina pediculus (?). 271 



At three o'clock a similar character prevailed; two, however, 

 of the vesicles having grown larger than the other two. 



At four o'clock the selfsame two larger ones had attained to 

 double the size of the two others, and one of them exceeded the 

 rest, and appeared to contain in its interior two rounded green 

 nuclei. The two smaller ones now hardly surpassed the rounded 

 green granules spoken of (fig. 4) . 



At five o'clock two large vesicles were visible, and one smaller 

 one of about one-fourth their size. The nucleus could still be 

 detected about the centre of the animalcule, by a delicate pellucid 

 outline, encroached upon and partly concealed by the peripheries 

 of the two developing cells of the interior (fig. 5). 



About six o'clock the two large vesicles had further augmented 

 in size, and occupied the greater part of the area of the entire 

 animal. One of these had in or upon it the two small granular 

 masses described. The outline of the original nucleus was still 

 perceptible. 



The two growing cells had now nearly come into contact, and 

 every minute hastened the apposition which presently occurred, 

 and in about another half-hour the two vesicles had blended 

 together, a constriction only indicating the previous line of sepa- 

 ration. Rather to one side of this constriction, and engaged 

 within the periphery of the coalesced cells, thus occupying nearly 

 the centre of the animal, the outline of a third vesicle could be 

 seen, probably the original nucleus. Again, on the side opposite 

 to the last vesicle — on that, viz. in which the gap of the mouth 

 was perceptible, — was another sac, overlying slightly the margin 

 of the large constricted coalesced cell, at the point of constriction, 

 and containing granules in its interior (fig. 6). 



The original rotundity of the animalcule had become, to some 

 extent, already interfered with by the development of the con- 

 tained cell ; but this interference was destined to proceed ; for 

 now the outer tunic began to protrude at one pole, in the long 

 axis of the enlarging interior cell, that is, in the direction in 

 which the latter exerted its outward pressure. This tendency of 

 the animal to increase in one direction continued, and an oval, 

 and afterwards a pyriform figure was attained. 



The two green masses, described in one of the now-coalesced 

 cells, occupied a position at the projecting part of the animalcule, 

 remaining distinct (fig. 7). 



The great cell would seem now to have undergone some de- 

 gree of contraction on itself, for it became more globular, the 

 constriction almost disappearing, and left a larger interval at the 

 opposite end of the animal to that from which it protruded. In 

 the meanwhile, the sac described as existing on the same side 

 of the animalcule as the mouth, increased rapidly in its dimen- 

 sions, so much so as to compress the larger one, forming for 



