“ They do not begin life as parasites, the females depositing their eggs on stones, plants, etc. They are animals of singular form and appearance. In the genus Aragulus there is a curious sucking disk on each side of the beak, or proboscis, although there are also jointed members terminated by prehensile hooks. ”

“ All are of small size, and attached either temporarily or permanently to the hosts on the juices of which they live, although many species have also the power of swimming freely in the water, some of their legs being adapted to this purpose. ”