STRUCTURE OF EXORKTORY ORGANS OF AMPHIOXUS. 495 



The methods pursued are of the most simple kind^ and it 

 is within the power of any one with living material at hand to 

 easily verify my results. The Amphioxus is pinned out on 

 its back in a shallow dish of sea water. The atrium is ripped 

 up with a needle along the mid-ventral line, and the two 

 metapleural folds pinned aside. The exposed pharynx is 

 then also ripped up with a needle, and portions of the right 

 or left side of the pharynx can then be torn out with forceps 



Figure of a portion of a section across the gill-bars showing the 

 excretory canal cut through. A. Atrium. C. Dorsal ccelom. 

 pb. Primary gill-bar. bv. Blood-vessel, ae. Atrial epithelium. 

 ce. Ccelomic epithelium. I. Lumen of the excretory canal, n. 

 Nucleus of a solenocyte. t. Tube of a solenocyte. Cam. and oil 

 immersion. 



and placed on a slide,^ care being taken to lay the outer 

 side uppermost. When covered and examined under the 

 microscope the general structure of the kidney can be quite 

 easily seen ; but the details which I am about to describe 

 can, unfortunately, only be made out after prolonged study 

 with the highest powers {-^ oil immersion and No. 8 eyepiece, 

 for instance). 



' §uch pieces can be stained and mouuted, or cut into sections. 



