538 THE GUINEA WORM. 
of moving their rings alternately, or they can proceed at a swifter pace by employing a similar 
mode of progress to that which is made use of by the larvee of the geometrical moths. Being 
furnished with a sucker at either end, they first fix their hinder sucker against any object, and 
then extend the body well forwards. Having secured the sucker of the head, they loosen 
their hold of the posterior sucker, arch their bodies just like the looper-caterpillars, and 
so proceed. 
Before bidding farewell to the Leeches, we must cast a casual glance at three remarkable 
members of this group. 
The first is the BRANCHELLION, or BRANCHIOBDELLA, a flattish and not very large creature, 
which is notable for being parasitic upon the torpedo, and retaining its hold in spite of the 
electric powers of the fish. Another species of the same genus is found on the lobster. 
The second of these creatures is the wonderful NEMERTES, a leech-like being not furnished 
with sucker, and attaining the extraordinary length of thirty or forty feet. 
The last of these beings is the LAND-LEECH (Hirudo zeylonica), a terrible pest to those 
who travel through the forests, and often occurring in such vast numbers as even to 
endanger life. 

INTERNAL WORMS; ENTOZOA. 
WE now pass to the last members of this great class, the Entozoa, or Internal Worms, 
so called because they are all found in the systems of living animals. They have also, but 
wrongly, been termed Intestinal Worms, inasmuch as very many species inhabit the respira- 
tory, or even the sensorial, organs, and are never found in the intestines. The Entozoa are 
very numerous, and are distributed throughout the world, inhabiting the interior of various 
living beings ; and, indeed, their presence is so universal, that wherever an animal can live, 
there are Entozoa to be found within its structure. 
To give an idea of the wide distribution of these strange beings, we will take one genus of 
Entozoa as exemplified by the specimens in the Museums, and note the various animals in 
which the members of that single genus have been found. 
The restricted genus Ascaris is the type of its family, and many specimens are in the col- 
lection of the Museums. Those have been taken from the following animals: man, mole, dog, 
fox, eat, seal, wood-mouse, sow, horse, grizzly bear, heron, tortoise (Several), toad, frog, ruffe, 
blenny, fishing-frog, barbel, cod (several), turbot, flounder, eel, goshawk, barn-owl, lapwing, 
red-wing, cormorant, and grouse. 
The history of these remarkable beings is, for the most part, shrouded in mystery, and we 
know but little of their true habits and the manner of obtaining entrance into the various 
beings on which they live. It is, however, ascertained that the young of the Entozoa have a 
very different shape from that of their parents, and that they may obtain entrance into their 
future homes under the disguise of various forms. 
To this curious sub-class belong many remarkable creatures, among which the following 
may be briefly mentioned. The Gutnea Worm (filaria medinensis) is one of the most 
developed of this group of animals. It is a strange-looking creature, eight or ten feet in 
length, and not thicker than ordinary sewing-thread. It is found in many of the hotter parts 
of the world, especially in the country from which it takes its name. It is also found in 
America, though it does not appear to be plentiful, except in the Island of Curacao. 
The Guinea Worm is much dreaded by the inhabitants of the countries where it resides, 
on account of the pain and inconvenience which it occasions, and the great difficulty in 
destroying it. It mostly takes up its residence in the leg, and there grows to an inordinate 
length, causing much pain and swelling until the head of the worm makes its appearance. 
As soon as the sufferer perceives that the worm has made its appearance, he takes a smal] 
