NO. 1788. NORTH AMERICAN ERGASILID^— WILSON. 293 



TTie Mdneys.— There are two excretory organs (d, fig. 13), one on 

 either side, lying near the lateral margins of the carapace and just 

 above the lateral lobes of the anterior end of the stomach, and 

 partially concealed by them. Each is a simple tube, coiled once into 

 a horseshoe shape, the long diameter of the coil at right angles to the 

 body axis. The coils differ somewhat in different specimens as can 

 be seen in figure 14, a and h. The bhnd end (posterior) of the tube 

 is a httle enlarged; the Other end is usually coiled once, in some 

 individuals around the blind end, in others free from it, and then 

 passes into the duct which leads forward and inward toward the 

 maxilliped, and apparently opens just 

 behind the base of the latter. This 

 organ was first described by Zenker as ^ 



opening near the mouth and probably a ^-^ ^ ^^ — -f 



poison gland; it was identified by Claus fig14._exceetory tubes of ergasi- 

 and Levdif' with the "schalendruse" of lus centrarchidarum. a and b, 



"■ ^ -, From DIFFERENT INDIVIDUALS. 



Phyllopods, and Claus showed that it 



opened on the base of the second maxillipeds in Phyllopods and 



behind the single maxilla in Cladocera, where it also opens in 



Ergasilus. 



These tubes can be seen in living specimens, but are usually in- 

 distinct, owing to the opacity of the contents of the body cavity and 

 the stomach. Often they can not be discerned at all, but occasionally 

 in freshly killed specimens they show up with great distinctness, 

 this being largely a matter of chance rather than skill. In such cases 

 the coiled tube and the duct leading from its anterior end can be 

 easily followed. The contents of the tube and duct are both color- 

 less and structureless. Furthermore the tube is not fastened in place 

 very securely, and frequently becomes displaced under pressure, 

 turning either backward or forward indiscriminately. On the 

 bursting of the body wall under continued pressure this kidney tube 

 passes out of the body with the first loose material that escapes. 



Accessory glands.— The only accessory glands to the alimentary 

 canal are what may be called the salivary glands, which surround the 

 esophagus for its entire length (fig. 15). These are made up of 

 elongated pear-shaped cells, the larger rounded ends lying nearest 

 the esophagus and the smaller pointed ends extending away from it. 

 The nuclei are large and spherical and stain deeply with hsematoxylin. 

 They lie in the larger ends of the cells, close to the esophagus. The 

 cells which are dorsal and ventral to the large nerve gangha are con- 

 siderably increased in size ; those which lie between the nerve ganglia 

 and the esophagus are smaller. 



There is apparently no arrangement into paired masses with a 

 distinct duct, but the cells are thrown together loosely and irregularly. 

 From their structure and staining, however, there can be no doubt 

 they are glandular in nature and that they contribute to digestion. 



