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POPULAR SCIENCE REVIEW. 
mistake into which I myself fell in my early study of these 
forms. Observing that many specimens of this species had 
little green egg-shaped objects adhering to their bodies, and 
knowing the egg-bearing habit of the species, I took for 
granted that these were the ova. At length, however, a 
specimen occurred with one or two manifest eggs, of much 
larger dimensions, and perfectly agreeing in form, colour, 
appearance, and proportions with the eggs of other Rotifera, 
adhering to the body, while the little green objects were there 
also. At length some of these latter, detaching themselves, 
swam away by means of their own cilia, and I perceived that 
they were parasitic Infusoria, of the genus Colacium, which 
ordinarily infest this species, as well as Entomostraca. Thus 
maturer observation corrects the errors of inexperience. 
One of the most remarkable forms of this order is the genus 
Asplarichna, so named because of a most strange and quite 
unparalleled deficiency in its organization. Furnished with a 
formidable pair of nipping jaws, a long gullet, a capacious 
lobed stomach, and a distinct pair of pancreatic glands, and 
being highly predatory and carnivorous, this animal has not 
the slightest vestige of an intestinal canal, the digestive stomach 
hanging like a globe in the centre of the capacious body-cavity, 
tied to various points of the walls by long elastic slender 
muscle-threads, which allow it to sway about. From the great 
comparative size of the animals — for they are among the very 
largest of Rotifera, — from the brilliant transparency of the 
skin, and from the smallness and paucity of the viscera in 
proportion to the capacity of the ample body, the organs can 
be determined and examined with unusual facility; so that I 
know of none that present so favourable opportunities to the 
student who wishes to demonstrate the anatomy and physiology 
of this charmingly crystalline tribe of animals. 
It is interesting to remark that the ovary in this genus is 
of the ordinary structure, though small. The young, however, 
are hatched, one at a time, within the body of the parent ; 
and an exceedingly curious and interesting spectacle is pre- 
sented by the young animal, perfectly formed, -with its eyes, 
its jaws, and all its other organs readily identifiable, occupying 
one-third of the volume of the parent, as it lies horizontally 
across the blunt sac-like extremity, occasionally working its 
jaws, and moving its viscera to and fro by means of its 
muscle-threads ; the double integument of the parent and 
offspring no more interfering with distinct vision than two 
thin films of glass. There is an outlet for the young at the 
period of birth, but it has no connection with the alimentary 
canal. 
In some of the species not the slightest trace of a foot is 
