You will receive 330ml of fresh water rotifers in a pouch like the above photos

Rotifers are small, mostly freshwater animals, and are amongst the smallest members of the Metazoa -- that group of multicellular animals which includes humans, and whose bodies are organized into systems of organs.
Most rotifers are about 0.5mm in length or less, and their bodies have a total of around a thousand cells. This means that their organ systems are a greatly simplified distillation of the organ systems found in the bodies of the higher animals.

A typical rotifer might have a brain of perhaps fifteen cells with associated nerves and ganglia, a stomach of much the same number, an excretory system of only a dozen or so cells, and a similarly fundamental reproductive system. They have no circulatory system.

It is an anomaly that despite their complexity, many rotifers are much smaller than common single-celled organisms whose world they share.

Their most salient feature, and the one which caused them to be named wheel animals by early microscopists, is the corona -- usually in the form of two lobes surrounded by beating cilia, which give a vivid impression of rapidly rotating wheels. When the rotifer is attatched, the current created by the corona brings food particles to the mouth, and when the rotifer releases the grip of its foot, they act as twin propellers, transporting the rotifer rapidly from one place to another.

Rotifers have at least two other remarkable qualities. Firstly, they are able to survive long periods -- even perhaps hundreds of years -- in a dried or frozen state, and will resume normal behaviour when rehydrated or thawed.
Secondly, they exhibit what biologists call cell constancy -- they grow in size not by cell division, but by increase in the size of the cells which they already have. In some species, the cells of a particular organ will merge together, forming a syncytium -- a cytoplasmic mass with interspersed nuclei. In any case, a rotifer ends its life with the same number of cell nuclei with which it was born.

Ecologically speaking, they play an important contributory role in the natural water purification process, since they feed for the most part on suspended organic particles and free-swimming algae, and are often present in large numbers.

With their highly transparent bodies, complex movements and varied lifestyles, rotifers are amongst the most fascinating creatures the microscopist can encounter.