112 COMPARATIVE ANATOMY. 



phroditic or unisexual. Of the former Helix (snail) is an 

 example ; of the latter, Paludina. A Fallopian tube passes 

 from the ovary, commonly lodged in or near liver, to the 

 uterine sac, at whose base lies an albumeniparous sac, while 

 at the point where it is continuous with the vagina, a recep- 

 tacle for semen is situated. The male genital organs consist of 

 a testicle, a vas deferens and an cjaculatory duct, which may 

 present a simple orifice, or open into a retractile penis often of 

 great size. With the hermaphroditic species the two kinds 

 of genital organs are more or less blended together, the 

 testicle with the ovum and the vas deferens with the Fallo- 

 pian tube. Every folliculus is double, and within the ex- 

 ternal, which contains eggs, an internal is enclosed, the 

 ova and sperm filaments thus lying in close juxtaposition. 

 Very often, also, the vagina is united with the ejaculatory 

 duct, forming a cloaca into which open several special secret- 

 ing organs. Both male and female organs are usually lined 

 with ciliated epithelium. (Siebold.) The genital pores may 

 be upon the right or left side. Extraordinary appendages 

 are seen to sexual organs in Helix (snail), consisting of a sac 

 opening near the outlet, containing numbers of dart-like 

 spiculse which, under sexual excitement and immediately 

 preceding coition, are successively ejected. 



In Ptcropoda the ovary and testicle are contained within 

 the liver and appear to be a single organ. In Phyllirhoe, a 

 genus of Heteropoda, the outer part of the single organ is 

 the ovary, the inner the testicle. The ova and spermatic 

 filaments mingle within, and impregnation occurs at the 

 lower portion of the oviduct. Penis of remarkable length 

 in Clio. 



Cephalopoda. The ovary is enclosed in a loose capsule, 

 into which from time to time the ova fall, to be conveyed 

 thence through an oviduct emptying at base of funnel on left 

 side of body near rectum. A glandular appendage furnishes 

 accessories to the egg. Placed upon ink-bag are two peculiar 

 bodies (nudimental glands) having a common outlet near the 

 orifice of the oviduct. They yield an adhesive substance 

 by which, after their expulsion, the eggs are fixed upon 



