XIX SYSTEMATIC 485 
of the stomach. These bodies generally appeared when the 
Tardigrades were kept in the same unchanged water for some 
weeks. Nothing certain is known as to their nature or origin. 
Systematic.—A good deal of work has recently been done 
by Mr. James Murray on the Polar Tardigrades and on the 
Tardigrades of Scotland, many of which have been collected by 
the staff of the Lake Survey.’ Over forty species have been 
deseribed from North Britain. 
The following table of Classification is based on that drawn 
up by Plate :— 
Table of Genera. 
I. The claws of the legs are simple, without a second hook. If there are 
several on the same foot they are alike in structure and size. 
A. The legs are short and broad, each with at least two claws. 
2-4 claws... . Gen. 1. ECHINISCUS, C. Sou. (Fig. 249). 
7-9 claws. .  Sub-gen. la. HCHINISCOIDES, Prater. 
B. The legs are long and slender ; each bears only one small claw. 
Gen. 2: LY DELLA, Doy. 
Il. The claws of the legs are all or partly two- or three-hooked. Frequently 
they are of different lengths. 
A. There are no processes or palps around the mouth. 
I. The muscular sucking pharynx follows closely on the mouth- 
tube. 
a. The oral armature consists on each side of a stout tooth 
and a transversely placed support. 
Gen. 3. MACROBIOTUS, C. Scu. (Fig. 252). 
f. The oral armature consists on each side of a stylet-like 
tooth without support. Gen. 4. DOYERIA, PiarE. 
II. The mouth- tube is separated from the muscular sucking 
pharynx by a short oesophagus. 
Gen. 5. DIPHASOON, Puate (Fig. 255). 
B. Six short processes or palps surround the mouth, and two others 
are placed a little farther back. Gen. 6. MILNESIUM, Doy. 
1. Genus ECHINISCUS (= EURYDIUM, Dovy.).— The 
dorsal cuticle is thick, and divided into a varying number of shields, 
which bear thread- or spike-like projections. The anterior end 
forms a proboscis-like extension of the body. Two red eye-spots. 
There are many species, and the number has increased so rapidly 
in the last few years that specialists are talking of splitting up the 
1 Tr. R. Soc. Edinb. xlv., 1908, p. 641. This contains a Bibliography of recent 
literature. See also Richters, Zool. Anz. xxx., 1906, p. 125, and Heinis, Zool. Anz. 
XXXilil., 1908, p. 69. 
