rilYUM .I.V.\A7.//M 91 



ill tlu' rcninii t'lttiii which the :ihm('iil;irv (•;iii:il h:i> liccii rclimvctl, 

 iiotinji; in each nu'laiiicrc an (•nlarnciiiciit , nr (jdnglion, and 

 Ihnr fxiirs of inriphcidl lurirs, two pairs leaving; tlic ^an^lion 

 directly, and a third appealing to h-avc the cord itself cej)hahid 

 of the ganglion. In the third or fourth seiiiiient note that the 

 two halves of the cord diverge to j)ass around the alimentary 

 canal as the cirrumphdniuqcnl rituj which unites dorsally with the 

 cerebral ganglion. Observe the pair of small peripheral iierves 

 given off from the IiiIoIxmI cerel)ral ganglion; these nerves divide 

 into very fine branches as they extend forward into the highly 

 sensitive prostomial region. Other peripheral nerves which 

 supply the ventral side of the cephahc end of the body are given 

 off from ihv circumpharj-ngeal ring. 



Label the parts of the nervous system on both the large and 

 small drawings of the plate. 



The Reproductive System. — A complete set of l)otli male and 

 female genital organs occur in the same individual. That is, the 

 earthworm is hermaphroditic. 



By careful dissection remove the intestine from about the sixth 

 metamere to the twentieth. Avoid cutting any organs which lie 

 below or to the side of the alimentary canal in the region between 

 the ninth and fifteenth mctamercs. 



Clear away the nephridia of the thirteenth segment and look 

 for the pair of ovaries, minute white bodies lying against the 

 septum at the cephalic end, near the nerve cord. By gently 

 waving the septum between the twelfth and thirteenth segments 

 the ovaries which look like tiny pears fixed at their broad ends 

 may be identified. When mature the ova drop from the ovary 

 into the ca'lom of the thirteenth segment and are pa.ssed out 

 of the body through a pair of nephridia which have become 

 modified into oviducts. The internal funnel-shaped openings of 

 the oviducts lie in segment 13, while the ducts penetrate the 

 .septum entering the c(elom of the fourteenth segment, where they 

 lead ol)li(iuely outward, opening to the exterior in this segment. 

 In the wall of each oviduct is an enlargement, the egg receptacle, 

 for the storage of eggs. 



Associated with the female genital organs are two pairs of small 

 white spherical bodies, the seminal receptacles, for the temporary 

 storage of spermatazoa received from the worm with which 

 reciprocal mating occurs. The.se are located in the ninth and 

 tenth .somites and open to the outside by two pairs of spi rmathecal 



