20 
animalcules suddenly jerk back into the tube simultaneously, 
and then again almost immediately emerge, the longer of the 
two with a perfectly formed upper extremity (fig. 9) ; the 
smaller one is a little later in perfecting the part. The 
whole process occupies about three hours. 
We have not yet done, however, with our Vaginicola. 
After a time it will be seen that one of the two, generally the 
smaller one, exhibits a delicate ring or band at about one 
third its length from the lower extremity. Sooner or later, 
after enjoying life in its ordinary condition for a day or two, 
it will retreat into its cell and become quiescent, leaving its 
companion still protruding and actively engaged in feeding. 
The cilia at the upper extremity now become absorbed, and 
there grow out from the ring or band before mentioned small 
filaments, which vibrate slowly. In about two hours it will 
present the appearance shown in fig. 11. When the cilia 
have attained sufficient length, the body begins to wriggle 
about until it finally separates from its attachment in the cell. 
It then turns completely round, so as to bring the base fore- 
most, and gently works its way to the mouth of the tube, 
where it squeezes past its companion, which still remains 
lolling out (fig. 12), and goes off swimming, a free and inde- 
pendent animal of the shape shown in fig. 13. It darts about 
rapidly, now fishing apparently among invisible animalcules, 
anon rolling along and waddling as if enjoying itself, occa- 
sionally darting off in a perfectly straight line and imping- 
ing with force upon a filament of Conferva, where it will 
remain for a time feeding apparently upon something found 
in the locality. This may go on for hours without any 
change in the aspect of the creature ; but frequently after 
one of its violent bumps against a piece of Conferva it will 
remain at the spot, and rapidly attach itself to the same by the 
front extremity (fig. 14). The action of the cilia now ceases, 
and they appear to become gradually absorbed. In a few 
minutes it stretches itself out, and again rapidly contracts, as 
if trying whether the attachment were perfect. In about ten 
minutes the form has assumed that given in fig. 15. The cilia 
appear as a rigid fringe, looking like the teeth of a comb. 
Every now and then the body contracts and again expands, 
and on each occasion the direction of the fringe is reversed. 
Anon will be perceived the formation of a delicate membrane 
(fig. 16) surrounding tlie entire organism (the new tube or 
case). After the lapse of twelve or eighteen hours the form 
assumes the appearance shown in fig.. 17. Cilia now begin 
to appear at the upper extremity, while the fringe of old cilia, 
v hich seems to serve the purpose of keeping expanded the 
