RESEARCH ON THE DIGESTIVE SYSTEM OF THE SCHIZOPODA 43 



Other bands of muscle run at various angles from the cuticle of the 

 œsophagus to the external integument of the animal. 



Tendons and internai skeleton. 



The Schizopoda are very rich in muscles that hâve undergone a 

 chemical modification and hâve become of a chitinous nature. 



In this way an internai rigid skeleton is formed to which are attached 

 various muscular bands. 



We hâve already pointed out in our anatomical descriptions the régions 

 where thèse chitinous bars are found, fig. 3, 6, 20, 33, 35, br. sk. 



In our préparations that hâve been coloured with blue carminé and 

 picric acid the différent degrees of transformation into chitinous substance 

 are very readily distinguised; the chitinous parts are of a brownish colour; 

 the parts that are still muscular are a deep green. 



Between thèse extrêmes ail the différent shades are found. 



This process is shown in fig. 43, which is a vertical section through a 

 band of muscular fibres that are undergoing a transformation into chitinous 

 substance. 



The transverse striations are very marked in m, but as the fibres ap- 

 proach the external cuticle cl, the transverse striations gradually disappear 

 A, whilst the longitudinal fibrils become more marked forming tendons 

 where they join the external cuticle, td. 



A portion of the myosarc is shown m. se. containing large nuclei. 



Such is the origin of tendons, apodemes and of the internai chitinous 

 skeleton ('). 



Proctodœal part. 



The epithelium of the intestine is formed of a simple layer of co- 

 lumriar cells lined by a thin cuticle at the anterior part of this région, 

 fig. 21. 



The protoplasm is filamentous ; the nuclei large. 



Outside the epithelial cells are the longitudinal muscle fibres m. /., 

 thèse are surrounded by the circular bands which are of greater strength, 

 situated at a short distance from one another. 



(') See IDE : Loc. cit. 



