21 



PLATE XI. 



THE EARTH-WORM— conan^ec^ 



Disposition op Internal Ougans- 



FlG. 1 aud DiAGEAM — 



, Mouth. 



Alimentary System. 



Cut end of muscular pharynx. 



Gullet. 



Crop, a dilated portion of gullet. 

 Gizzard, wliitish, thick, and muscular. 



Intestine leading straight to anus, and covered with a brownish 

 mass supposed to be the liver. 

 / Colourless corpuscles in perivisceral cavity — two shown. 

 Pseud-haemal vessels contractile, and therefore circulatory — 

 Supra-intestinal vessel (L. supra, above). 

 Sub-intestinal vessel (L. sub, under). 

 Sub-neural vessel. 

 Blood System — Circulatory j Commissural vessels connecting supra-intestinal and sub- 



AND Respiratory . . \ intestinal vessels. 



Dilated commissural vessels in the region of the reproduc- 

 tive organs, the so-called liearts. 

 Coloured fluid without corpuscles contained in pseud-hsemal 

 vessels acts as an oxygon-carrier, and is therefore respira- 

 tory in function. 



Eenal System Segmental organs in pairs in each segment. 



Cerebral or prre-oral ganglia connected by commissural cords 

 embracing the pharynx with the 

 Nervous System . . . . <^ Sub-oesophageal or postoral ganglia whicli form tlie anterior 



extremity of a 

 Chain of ganglia extending to end of body. 



T, CI f Ovaries and oviducts. 



Reproductive System . . i ^ , , . . , . ^ 



( iestes and vasa deierentia shown in fig. 2. 



Figs. 2, 3, 4. Renal and Reproductive Systems — 



Segmental organs with internal ciliated opening and external pore (tig. 3). 



f Anterior pair of spermathecse. 



( Posterior pair of spermathecoe. 



f Anterior pair of bilobed testes. 



( Posterior pair of testes. 



(■ Anterior reservoir of testes with duct. 



[ Posterior reservoir of testes with duct. 



Common vasa deferentia. 



Capsulo-genous glands for secreting egg-capsules. 



OvariK!. 



Oviducts with wide ciliated internal opening and external opening (fig. 4). 



Fig. 5. Ovary with ova. When laid the eggs are enclosed in clusters within a chitinous case, each egg 



consisting of — Vitelline membrane, 



Vitellus. 



Germinal vesicle. 



Germinal spot. 



Spermatozoa from Spermatheca. 



Classification — 



Sub-Kingdom — Annelida (L. annuhis, a ring), because the body is segmented ; without jointed 



limbs ; nervous system forms a ring round gullet, followed by a ventral chain of ganglia. 



Natural Order — Oligochas'ta (Gr. oligos, few ; chaite, hair), because the bristles are in vows, not 



tufted. 



Genus — Lumbricus. 



Common Name — Earth-worm. 



