434 NATURAL HISTORY MISCELLANY. 
may share their prey in common. The digestive canal is oceu- 
pied by the following Coinosites : —Fierasper, Stegophyle, Stylifer, 
Phronimus, Hyperia, the mantle by Pinnotheres and Pagurus, the 
exterior ds Myzostoma, Cyamus, Pycnongonon, Caprella p 
Cheetogaste 
-~ The true psa e cannot live without assistance ; they are di 
visible into several categories. Some, such as the leech, fleas, 
and some dipterous insects, suck the blood of their victim, and 
then quit him to take their after-dinner nap in the open air; 
others, such as the ichneumon flies, do not quit their host till they 
have become adult, and have in the process exhausted the last 
drop of blood of their unfortunate prey. The greater number 
lead a free life when young and merely attach themselves to a host 
at the time of TS such are the Bopyrian and Lernæan 
Crustacea. There is a further very interesting group, who enter 
a host while ‘yet Seii simply in order that they may get car- 
ried by its means into a second host, where they will ripen 
their eggs. Often whilst waiting in their first host (sometimes 
vainly waiting, no doubt) for him to be devoured by their second 
and ultimate victim they reproduce agamically. Such parasites 
are the Flukes and many Tapeworms. ‘These divisions are p 
tabularly set forth :— 
Parasites free. bi 
7 a ice DS ae 
during all their life. during a part of their life they pass through 
~—— F $m 
Leeches. ` a single host. several hosts whilst immature. 
Fleas and Flies. —— = ~ 
Caligus. gims im- = ma- 
Distomata. 
Cestoids. 
Barera errei, 
Mermis. Lernæans. x 
` The parasites of the first category which i free during al 
their life, Professor Van Beneden calls Ph s, and co wale 
them to the habitués of a hotel who avail asiti of the 
@héte, but do not have a bedroom in the building. The oe 
parasites which have both board and lodging are divisible in 
three principal categories. 1st. Xenosites—who are pil 
transit — voyaging with a distinct but distant object os r 
ns as t 
