REPRODUCTIVE SYSTEM. Ill 



tion of reproductive organs varies; each organ is composed 

 of simple or branched tubes, with proper excretory ducts; 

 these last are sometimes wanting, when the contents of the 

 former escape by rupture, and, falling into the cavity of 

 the body, pass out through the respiratory openings. (Sie- 

 bold.) Copulatory organs absent. In Toxopneustes (sea- 

 urchin) the organs fill up the interspaces between rows of 

 ambulacral vesicles. Holothuria is bi-sexual. The ovary is in 

 the form of slender tubes floating freely in the cavity of the 

 body, the efferent canal (oviduct) opens upon the back in the 

 neighborhood of the mouth, below the osseous rings, between 

 the tentacles. Peculiar appendages to oviduct seen in the 

 form of so-called yelk glands. Male apparatus closely re- 

 sembles the above. In Synapta the testes and ovaries are in 

 one tube; the eggs become impregnated by being pressed 

 against the sperm cells. 



MOLLUSCA. Polyzoa. With the hermaphroditic Polyzoa 

 a ribbon-like ovary and testicle are suspended from the ex- 

 tremity of the stomach. In these organs are developed only 

 two to four eggs or fasciculi of spermatic particles from cells 

 arranged like a string of pearls. (Siebold.) The sexual ele- 

 ments are probably voided through tentacles. 



Brachiopoda. In the unisexual Brachiopoda two pairs of 

 ovaries and testicles are developed between mantle and the 

 lining membrane of the venous sinus. The method of escape 

 is unknown. 



Tunicata The Tunicata, excepting the solitary Ascidians 

 and Salpa, are hermaphroditic. The former may be self-im- 

 pregnating. The organs are situated between the branchial 

 chamber and mantle. 



Lamellibranchiata. Rarely hermaphroditic, as in Cyclas. 

 The male or female organ is placed in relation with the liver, 

 and beneath the mantle. The oviduct empties in or about 

 the renal sac. When the foot is largely developed, the testicle 

 is commonly placed within the interior of the base, while the 

 vas deferens, toward the base of foot when present, or near 

 mouth, as in Oslrea (oyster). ISTo copulatory organs. 



Gasteropoda, The Gasteropoda may be either herma- 



