458 ALDEN B. DAWSON 



The configuration of the cavity of the cloaca, the arrangement 

 of the glands and the positions of the ciliated areas make the 

 theory of spermatophore formation in Necturus seem plausible 

 and tend to stimulate speculation. The mucous secretion of 

 the cloacal gland when liberated into the ventral trough would 

 be gradually moved caudally b}^ the cilia on the ridges and would 

 eventually collect in the cloacal chamber and the ventrolateral 

 recesses projecting from it. In this position the mass of mucous 

 material would probably be increased by additional secretion 

 from the cloacal tubules which terminate on the internal papillae. 

 Dorsolaterally in the cloacal tube, the ripe sperm would be ex- 

 pelled from the urogenital ducts and the median dorsal ciliated 

 area would carry them back until they became mingled, first, 

 with the secretion of the median cephalic portion of the pelvic 

 gland and later with the secretions of the lateral and caudal 

 portions of this same gland. By this time the sperms would be 

 in the dorsal groove and far enough caudad to be caught up by 

 the moving mass of mucous secretion which is propelled caudad 

 by the cilia of the ventral ridges. In this manner a spermato- 

 phore, having as a base a mass of mucous secretion and bearing 

 on its dorsal surface spermatozoa mingled with secretion from 

 the pelvic gland tubules, might be formed. The final solution 

 of this problem must await direct observation in the field. 



Early writers attempted to homologize the cloacal glands of 

 urodeles with the prostate and bulbo-urethral glands of the. 

 higher mammals. Any such homology has been denied by Hei- 

 denhain ('90) and Kingsbury ('95). In attempting to discover 

 homologies it seems unwise to begin with what are obviously 

 specializations of some more simple arrangement, and the pros- 

 tate and bulbo-urethral glands doubtless represent such special- 

 ization. A more primitive condition is seen in both monotremes 

 and marsupials, in which urethral glands, tubular glands occur- 

 ring in the wall of the urogenital canal, are abundant. In mono- 

 tremes there is a common cloaca with a primitive penis project- 

 ing slightly from its ventral wall. From this simple organ it is 

 believed the typical penis of mammals has been derived and it is 

 also regarded as homologous with the intromittent organ of 



