RESISTANCE OF RHABDITIS TO ACIDS. 97 



Rhabdites were placed in a small quantity of neutral red solution 

 on a slide, and were observed under a microscope. The stain 

 entered tli rough the mouth, and soaked out through the wall of 

 the esophagus. In one worm the stain entered through the anus, 

 but only a Miiall region of the posterior part of the body was 

 stained. 



A solution of neutral red, which stained dead worms deeply, 

 stained living worms only faintly; a strong solution, then-fore, 

 was used. Staining for 2.5 hours in such a strong solution, 

 the anterior part of the body as faras the second bulb was 

 deeply stained, but in the remaining part the intestine only 

 was colored. The intestine was stained less deeply than the 

 anterior regions of the body, and the stain became progressively 

 lighter toward the posterior end. This seems to show that the 

 >t.iin entered through the mouth, but not through the cuticle 

 nor through the anus. After staining for 20 hours the worms were 

 >till alive, and the anterior regions a little beyond the bulb'of 

 the esophagus were deeply stained. In the remaining part the 

 intestine only was colored, and its posterior regions were stained 

 less deeply than its anterior regions. 



Such stained worms were placed in a weak solution of XaOH, 

 and then the alkali entered through the mouth, and proceeded 

 towards the interior. In about 20 minutes the portion of the 

 body as far as the second bulb became yellow, but the change in 

 color did not go further. Later a rapid diffusion of NaOH from 

 the posterior end anteriorly was observed, and thus the entire 

 body of the worm changed to yellow; the alkali seemed to enter 

 through the anus. In another worm the change in colour pro- 

 ceeded anteriorly starting from the anus. 



To show definitely that the cuticle prevents the entrance of 

 the stain and the XaOH, the posterior regions of some w< inn- 

 were cut off. Then the stain entered through the mouth and ilu- 

 cut end. Such worms were, therefore, Mained in toLo for 4 

 hours, and at the end of this time they were still alive. Contrary 

 to the case of uninjured worms the change in color carried by 

 ViOH began at both ends, and proceeded t,i-ter anteriorly from 

 the cut end than from the mouth. In about one hour and three 

 quarters the change in color has been completed in such injured 

 worms. 



