Natural History of the Animalcules. 99 
generative system to ensure the propagation of the specific 
form : all equally elaborate, interdependent and wonder- 
ful. In the Animalcules we find an entire absence of 
each and all of these systems. A " body" is certainly 
present, consisting in the lowest forms of a minute speck 
of simple outline, and in the higher forms taking on a 
complicated and often thickened outline, more or less 
supported by an external covering or shell, fun6lionally 
a skeleton ; but, in all, the interior consists either simply 
of the jelly-like protoplasm, or of protoplasm variously 
thickened by oily globules or granules, or marked by 
fluid spaces, or more particularly by a denser, jelly-like 
mass known as the nucleus. 
In a few forms, a simple aperture or mouth, leading by 
a simple canal or gullet into the soft, central, jelly- 
substance of the body, represents the beginning of a 
digestive tra<5l ; but usually food is taken in, and refuse 
thrown out, at any part. In some others, a small globule 
of liquid which forms and bursts rhythmically, represents 
some very rudimentary type of a circulatory or excretory 
organ ; while, in still fewer forms which are stalked, the 
stalk contains a contraftile fibre which may be taken to 
represent a rudimentary muscular fibre. Sensation takes 
place by the general margin of the protoplasm or by 
variable and temporary extensions of its substance, or by 
fine, hair-like or whip-like threads which are permanent 
extensions of the body, and these serve also as locomotor 
and prehensile organs, taking the place of arms and legs, 
seizing food when it is at hand, causing currents in the 
water in which the organism lives, so that food is brought 
within reach, and giving rise to moments for progression. 
No sexes can be distinguished among these minute beings ; 
N2 
