Peripatus. 
119 
the most gifted naturalists of his time, had the opportunity of Wall-case 
dissecting freshly killed specimens at the Cape of Good Hope. on p P 10) 
When opened under water a glistening appearance revealed 
the presence of air-tubes, such as are found among insects, spiders 
and centipedes, and nowhere else in the animal kingdom ; but, 
whereas in these three groups the air-tubes (or tracheae) are 
supported by a spiral coil of chitin which keeps them open after 
preservation in spirit, those of Peripatus are not so supported. 
Fortunately also this Peripatus was viviparous, and, as the 
anatomical drawing in the case shows, a number of eggs were 
found in the oviduct ; these are in various stages of development : 
following them out Moseley was able to see that the first of the 
appendages are converted into mouth-organs. This is a character 
which distinguishes the centipede from the ringed worm, and so far 
settled the question of the relationship of Peripatus. But Moseley 
did more than this, he showed that Peripatus belonged to that 
division of the Arthropoda which is known as Tracheata, and 
which consists of scorpions, centipedes, flies and their allies. 
During the last quarter of a century much attention has been 
paid to the Onychophora, of which more than 50 species are 
now known. 
Peripatus is to be found in moist and shady places. It avoids 
light, and is nocturnal in its habits. On irritation, it shoots out 
fine threads of a tenacious milky fluid, not unlike the threads of a 
spider’s web. This fluid is sticky enough to hold fast flies. In 
moving it never wriggles, but has a gait extremely like that of a 
caterpillar. 
There are a number of more or less minute characters by 
which the species are distinguished from one another. The most 
remarkable difference perhaps is in the characters of their eggs. 
In the Neotropical species, represented here by P. juliformis, the 
egg is minute, and almost entirely devoid of yolk. In the Gape 
species (. Peripatopsis capensis) the eggs are larger and there is 
some yolk. In the eastern species (e.g., Eoperipatus horsti) the 
egg is large, and there is a quantity of food-yolk. One at least of 
the Australasian species lays eggs, which are hatched outside the 
body. The species vary further in the number of legs, and also in 
the constancy or inconstancy of the number ; that is to say, some 
species have a definite number of legs, while others vary consider- 
ably in the number that they possess. 
The group is of great scientific interest as a clear link between 
Arthropods and Polychaete worms. 
