STUDIES IN EARTHWORM CHLORAGOGUE. 89 



worm 5 mm. long and continuing through increasing sizes till a 

 stage was reached in which the chloragogue cells appeared fully 

 developed. In the smallest worms the peritoneal layer, the 

 chloragogue that is to be, is always apparent and a similarity is 

 evident between it and the peritoneal layer elsewhere, both in 

 structure and in reaction to staining fluids. In the smallest 

 worms the chloragogue appears as a simple layer as yet undiffer- 

 entiated into the club-shaped cells of the adult form. In larger 

 specimens of the series a gradual development into the typical 

 chloragogue cells can be traced. As the cells become older they 

 increase in length, the characteristic granules appear and they 

 become less and less responsive to stains, until in the fully de- 

 veloped adult condition they are practically proof, excepting their 

 nuclei, against every stain to which they were subjected. The 

 nuclei readily respond to stain. 



Upon adult worms the following experiment was performed to 

 determine whether there was any renewal of chloragogue when 

 it is artificially removed. With a sharp razor an incision was 

 made through the outer body wall into the ccelomic cavity, 

 exposing the alimentary wall. With a scalpel the chloragogue 

 was then removed from the alimentary wall as completely as 

 possible and the worm afterward kept under favorable conditions 

 of temperature, moisture, etc., in order to insure a condition of 

 thrift. The result of this experiment was that although the 

 wound made in the body wall in order to remove the chloragogue 

 began to heal well the second day after it was made, no chlora- 

 gogue regeneration was observed in specimens sectioned at vari- 

 ous intervals thereafter. 



II. Distribution. In the adult worm the chloragogue is found 

 to be distributed as follows : beginning at the posterior end of 

 the oesophagus it extends dorsally, attached in abundance to 

 either side of the dorsal blood vessel as far back as the thirtieth 

 segment (counting from the rear). It is interesting to note that 

 the chloragogue attached to the outside of the alimentary canal 

 practically ends in the region where the typhlosole ends : from 

 the thirtieth segment to the anus it becomes less and less abun- 

 dant, finally disappearing about the seventh somite. In the 

 typhlosole it is also abundant. Somewhat less abundant than 



