REPRODUCTIVE ORGANS 353 



In the females, as in the males, of cyclostomes and teleosts the reproductive 

 ducts are not easily brought into harmony with those of other vertebrates, and 

 an answer to all questions cannot be had until the development of the parts has 



jcen studied in more forms, and especially the ganoids and dipnoi. In the 

 cyclostomes the eggs are shed from the ovaries into the coelom and are thence 

 passed outward through the abdominal pores. 



In the teleosts there are several conditions. The ovaries may be simple 

 and solid bands or saccular in character with an internal lumen (fig. 375, E). 

 In the first the eggs pass into the coelom and thence to the exterior by abdominal 

 pores or by oviducts of varying lengths (fig. 375, F). Concerning the nature 

 of these ducts there is uncertainty. They may be true Miillerian ducts or new 

 formations within the group. The fact that similar tubes occur, with perma- 

 nently open ostia in both sexes of the sturgeons (fig. 373, ^), and that these open 



lehind into the Wolffian ducts, lends probability to the view that the ducts of 

 the ordinary teleosts are Miillerian in character, but greatly modified. 



The saccular condition of the ovaries appears to arise in two ways. 

 In the one the primitively free edge of the ovary bends laterally and 

 fuses with the coelomic wall, thus enclosing a cavity, the parovarial 

 canal, closed in front. In the other type a groove of the covering 

 epithelium forms on the surface of the ovary. This closes over and 

 sinks inward, forming what is termed as an entovarial canal. Either 

 canal may extend backward to the hinder end of the body cavity, thus 

 forming an oviduct, or the oviduct may be formed from both kinds of 

 canals, one in front, the other behind. From this it would appear 

 that the ovary originally extended back to the hinder end of the 

 coelom (as it does in Cyclopterus) or that the par- or entovarial 

 canal had united with a Mullerian duct which has otherwise been 

 entirely lost. The oviducts thus formed usually unite before open- 

 ing to the exterior, either directly or via a urogenital sinus. The 

 oviducts in the dipnoi (fig. 375, A) are much like those of the 

 selachians, emptying independently into the cloaca. They persist, 

 though of small size, in the males (fig. 373, D). 



CoPULATORY Organs 



In many vertebrates the eggs are fertilized after passing from the 

 oviducts to the exterior. This is the case with the cyclostomes, most 

 fishes, with the exception of the elasmobranchs, and with many 

 amphibians. In other groups (including some teleosts) fertilization 

 is internal. In some cases the transfer of the sperm from the male 

 to the female is effected by the apposition of the cloacae of the two 

 sexes, but in others copulatory organs of an intromittent character 

 23 



