TR ACHE AT A 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 enlsirged, 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 whien 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 

 pair of legs, and there are no genital papillae; the ovary 

 is double, and the spermatophores are 1\ 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 hoUow 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 MoUusca. 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 



