454 ALDEN B. DAWSON 



All pelvic tubules terminate in low papillae. At the bases of 

 these papillae shallow circular depressions are usually observed 

 recalling the structure of the circumvallate papillae of the tongue. 

 In some regions papillae are indistinct and only barely recogniz- 

 able. The tubules of the large median caudal division, for the 

 most part, open upon the walls of the median dorsal groove 

 (figs. 13, 14, 15). The more cranial tubules of the lateral pelvic 

 differentiations open on the dorsal walls of the so-called longi- 

 tudinal furrows (figs. 12, 13), while the most caudal ones are 

 found to open upon a middorsal region, the caudal end of the 

 stem of the Y-shaped area previously described (figs. 11, 12). 

 The short tubules of the median cephalic group terminate on 

 the middorsal region which forms the cranial portion of the stem 

 of the Yrshaped area (fig. 10). 



In comparison with the cloacal and pelvic glands, the abdomi- 

 nal gland in Necturus appears almost vestigial. It is divided 

 into two masses which lie near the caudal end of the cloacal ori- 

 fice and dorsolaterally to the paired external papillae (figs. 2, 3, 

 abd.gl.). The tubules which compose this gland are short and 

 greatly convoluted and possess a characteristic epithelium which 

 distinguishes them definitely from the other tubules of the cloa- 

 cal mass (fig. 16). They open mainly on the medial surfaces of 

 the external papillae, but a few are also found to open along the 

 inner margins of the cloacal lips. 



b. Muscular layers and dorsal ganglion 



The muscular coat consists of two layers of smooth muscle 

 which, in the extreme cephalic portion of the cloacal tube, are 

 sharply differentiated into an inner circular and an outer longi- 

 tudinal layer (figs. 7, 8). Further caudad, however, this definite 

 arrangement is more or less disturbed by the presence of a large, 

 dorsal, ganglionated plexus and the numerous tubular glands. 



The dorsal ganglion represents a local enlargement of a por- 

 tion of the sympathetic nervous system, being apparently a 

 caudal continuation of the myenteric plexus of the intestinal 

 tube (figs. 9, 10). From the ganglion small bundles of nerve 

 fibers pass caudally to the various cloacal glands. 



