368 MR JAMES MURRAY ON A NEW FAMILY 
through all three cervical segments. The eyes, when present, are in the rostrum, near 
its tip, or on the back of the brain. The mastax, containing the jaws with their teeth, 
is in the third cervical or first central. The stomach extends through all four central 
segments, which also contain the ovaries and the eggs or young. The pre-anal contains 
the intestine, the anal the contractile cloaca. The foot-glands occupy all the joints of 
the foot, and may extend into the anal, or even into the pre-anal. The toes are three 
or four in number, or they are united to form a disc, which is perforate with pores for 
the passage of the mucus. 
The corona of the Philodinadze consists mainly of two nearly circular discs, borne 
on pedicels. The principal wreath borders the discs. The secondary wreath runs 
round the bases of the pedicels from back to front, and merges in the cilia of the mouth. 
Near the centre of each disc is in many species a seta, or pencil of sete, or several short 
motile cilia, which usually rise from a small papilla or a larger process. The lower lip 
is the central portion of the under side of the mouth, and is shaped likea V. The upper lip 
is the space between the bases of the pedicels and the front of the rostrum. Its form is 
very characteristic for each species. Its most important structures are two folds of skin, 
which continue those prominences at the sides of the mouth known as the collar. 
These folds run round the bases of the pedicels, close to the secondary wreath, and may 
meet in the middle line just in front of the rostrum, or may terminate at some distance 
apart, in processes of various form. In the middle line, between the pedicels, is often 
found a peg-like process, known as a ligule. The water-vascular system, with its 
vibratile tags, usually about six pairs, is dificult to observe. The number of pairs of 
tags seen is always noted, though this may not be the full number present. 
The skin may be smooth and hyaline, stippled with pellucid dots, viscous, papillose, 
or variously warted or spiny. The back and sides of the trunk are longitudinally 
plicate. The ventral side is obscurely transversely plicate. In a few species the 
ventral transverse folds are numerous and deep. 
Halits.—The great majority of the known species are free and independent animals. 
None are truly pelagic. Even those which are in the habit of swimming only do so for 
short distances, and in the shelter afforded by mosses and other water plants. Those 
which do not swim creep in caterpillar fashion on the plants among which they live or 
on the mud of ponds. When feeding they anchor themselves by the foot. The 
Adinetadee and some Callidine can also glide forward by the action of certain cilia— 
in the Adinetadee those of the corona, in the Callidine those of the rostrum. Several 
species secrete protective cases ; others accumulate irregular tubes of débris. 
Parasitism.—A number of species are ectoparasites upon other animals. None are 
internal parasites or feed upon their host. They are commensals or messmates. They 
attach themselves by the foot to some crustacean, insect larva, or other animal. They 
seem to desire from their host only protection, conveyance from place to place, possibly 
a Share of food. Ased/us is a favourite host, and often carries several species together, 
All the Bdelloids known to me which have taken to the parasitic mode of life are large 
