Sie =" 
480 TARDIGRADA CHAP. 
evaporates when desiccation takes place, and is soon replaced after 
rain; it forms no coagulum when reagents are added to it, and 
it probably differs but 
little from water. Float- 
ing in it are numerous 
corpuscles, whose number 
increases with age. In 
well-fed Tardigrades the 
corpuscles are packed 
with food-reserves, often 
of the same colour—green 
or brown—as the con- 
tents of the stomach, 
which soon disappear 
when the little creatures 
are starved. 
The alimentary canal 
begins with an oral cavity, 
which is in many species 
surrounded by chitinous 
rings. The number of 
these rings and _ their 
general arrangement are 
of systematic importance. 
The oral cavity opens 
behind into a fine tube 
lined with chitin, very 
characteristic of the 
Tardigrada, which has 
been termed the mouth- 
Fic. 252.— Macrobiotus schultzei, Gr., x 150. tube. By its side, eon- 
(Modified from Greeff.) a, The six inner papillae 
of the mouth; #, the chitin-lined oesophagus; VETSINg anteriorly, he the 
c, calcareous spicule; d, muscle which moves two echitinous teeth, which 
the spicule; e, muscular pharynx with masti- a 
cating plates; f, salivary glands; g, stomach; May Open ventrally into 
h, ovary; 7, median dorsal accessory gland ; the mouth-tube, as in 
> 
k, diverticula of rectum. Maneater hufelandi 
and Doyeria simplex, or may open directly into the oral cavity, 
as in Hehiniscus, Milnesiwm, and some species of Macrobiotus. In 
some of the last named the tips of the teeth are hardened by a 
calcareous deposit. The hinder end of each stylet or tooth is 
