116 COMPARATIVE ANATOMY. 



those of insects. Coition always occurs. Copulatory organ 

 of male frequently complicated.* 



VERTEBRATA. Pisces. Ovaries (roe) generally double. 

 Single in many cartilaginous fishes, and in Perca (perch). 

 In Amphioxus, Anguilla (eel), and Salmo (salmon), the ovaries 

 are without oviducts. They are either 'adherent by one side 

 to the walls of the abdominal cavity,' or engaged within 

 loose festoons of the peritoneum. The eggs are discharged 

 into abdominal cavity, in all probability, to escape by minute 

 pores placed one on either side of the median line immedi- 

 ately behind the anus. In marsipobranchiate fishes and 

 Acipenser (sturgeon) the eggs, after escape, are received 

 into short incomplete oviduct. In Selachia the ovaries are 

 placed at the anterior portion of abdomen, and are distinct 

 from oviduct. The latter is dilated at its inferior portion into 

 a longitudinally plicated chamber, which is analogous to a 

 uterus. A somewhat similar dilatation is met with in Blen- 

 nius vivaparus and Anableps. In osseous fishes the ovaries, 

 which are relatively of great size, are more defined, and en- 

 closed within a capsule. They communicate directly with 

 the oviducts, so that the eggs may be said to be discharged 

 internally, thereby differing from all other vertebrates. The 

 oviducts may unite, as in Clupea (herring), or proceed sep- 

 arately to terminate at a common genital pore. 



Between the external form of the testicle (milt) and ova- 

 ries of most fishes no prominent distinctions exist. The 

 sperm cells are arranged within a cellular matrix and with- 

 out seminal ducts, as in Amphioxus, marsipobranchiates, and 

 Pleuronectes (flounder). The cells line terminal ends of coiled 

 tubes, which often join the excretory duct, as in majority of 



* " Spiders use their hollow, spoon-shaped palpi in copulation. These are 

 filled with sperm and applied to the entrance of the vulva. For this pur- 

 pose, the last article of the palpi, which is always hollow and much enlarged, 

 contains a soft spiral body terminated by a curved, gutter-like, horny pro- 

 cess. Besides thia, there is an arched, horny filament, and several hooks, 

 and other appendages of the most varied forms. These are protractile, and 

 serve, some to seize the female, and others as conductors of the sperm." 

 (Siebold.) 



