TRACHEATA 307 
Certain glandular structures, known as crural glands, occur 
in every pair of legs except the first; they consist of a vesicle 
placed in the lateral portion of the body-cavity, and lined with 
columnar cells; this communicates with the exterior by a short 
tube. The crural gland of the seventeenth pair of legs is in the 
male enormously enlarged, and reaches forward as a tubular 
diverticulum as far as the ninth pair of legs; its exact function 
is unknown. 
A pair of slime glands lie in the central division of the body- 
cavity ; each communicates with a reservoir which opens by a 
duct on one of the oral papillae. They excrete a sticky slime, 
which is ejected with some force when the animal is irritated. 
In Peripatus Edwardsii, a South American species, the 
crural glands are absent in the female, and only occur in the 
male in two segments; the genital opening is between the last 
par of legs, and there are no genital papillae; the ovary 
is double, and the spermatophores are 13 inch long. The 
stigmata are irregularly scattered. In Peripatus Novae Zea- 
landiae the tracheae are said to be branched. 
The importance of Peripatus is twofold: in its structure 
it combines features of two or three different phyla, and the 
history of its developement has done much to explain the more 
peculiar characteristics of Arthropod structure, and to bring 
these animals in line with what is known of other groups. 
Both its distribution and its structure point to its being 
a very archaic form. The arrangement of its nervous system, 
the sympathetic nerves, the muscular pharynx, the structure 
of the eyes, the serially repeated nephridia, the com- 
paratively short stomodaeum and proctodaeum, the thinness 
of the cuticle, and the hollow nature of the appendages, are 
all features which are naturally associated with the Chaeto- 
poda; some of these features are also met with in the more 
primitive Mollusca. On the other hand, the segmented 
appendages, the modification of some of the appendages as 
mouth organs, the presence of antennae, the tracheal nature 
of the respiratory organs, the structure of the heart and of 
the generative organs, are all features shared in common by 
the Tracheata and many by the Arthropoda in general. Thus 
Peripatus combines some of the more important characteristics 
