ONYOHOPHORA OF WEST AUSTRALIA. 



375 



INTERNAL ANATOMY. 



Alimentary Canal, etc. 



The a.liinentary canal presents nothing of exceptional import- 

 ance in the way of dift'erences from the conditions observed in 

 other species of Peripatiis. The jaws have aU'eady been desci'ibed. 

 A few words are necessary with regard to the mnscles attached 

 to them. It is frequently stated that the muscles of the man- 

 dibles are the only striped muscles in Peripatus. A careful 

 examination of all the muscles in the West Australian Peripa- 

 toicles has been made, but so far as transverse striation is con- 

 cerned no differences can be made out between any of tliem. No 

 mnscles be;ir cross-stripes, all appear smooth. 



•Salivary Glands. 



Two well-developed salivary glands are present, opening by a 

 common duct ventrally into the mouth. The common median 

 duct is very short (see PI. I. iig. 1) and gives rise almost at once 

 to two narrow tubes which run out at right angles to the long 

 axis of the body a,nd then bend suddenly backwards when the 

 lateral body-wall is reached. This portion (PI. I. fig. 1, Sal.G.d.) 

 is non-glandular, and the w^alls consist of compact cubical cells. 

 A marked change takes place when the ducts bend abruptly back- 

 wards to run in the lateral compartments in close proximity to 

 the nerve-cord ; the ducts pass here into the glandular region 

 (PI. 1. fig. 1, Sal.Gl.) of the salivary gland. The cells of this 

 part are often much vacuolated, and the nuclei are pushed to the 

 bases of the cells, where they lie in close ])roximity to a thin 

 muscle and connective-tissue sheath (see PI. II. fig, 5). 



The length of the salivary glands is such that they extend back 

 to somewheie at)Out the 7th or 8th pair of legs — -that is to say, 

 just beyond the middle of the bod}^ 



The Tbache.e, 



The respiratory organs of Peripatus have always been regarded 

 as of special note in view of the interesting relationships of the 

 Onyciiophora. It is somewhat surprising, then, to find that even 

 to-day there is some doubt as to whether a spiral libre is present 

 in the tracheal vessels. Other points are a-lso uncertain. 



The respiratory organs, as is well knovi^n, consist of tracheie. 

 These are very delicate and of minute diameter. In the West 

 Australian Feripatoides they could only be made but with difii- 

 culty in preserved specimens, although more easily in sections. 

 They are, however, exceedingly clear when freshly killed speci- 

 mens are dissected under wate]- and examined with a Zeiss 

 binocular dissecting microscope. Ample material has rendered 

 this mode of examination possible. 



DistrihUion of TracJtece. — As is well known, tlie trachea^ of 



