ANNELIDA OR ANNULATA m 



Polynoe have pale yellow blood; but in Sabella It is an olive green. 



The nervous system is well supplied with blood, having two 

 lateral neural and one subneural vessel for the nerve cord. At room 

 temperature (i2°-i8° C.) in Lumbricus terrestris, the dorsal vessel 

 pulsates about fifteen to twenty times per minute, and in Nereis 

 (marine sand-worm) it is about eight times per minute. Respiration 

 is osmotic. There are many capillaries under the cuticle. 



Excretion. — Paired nephridia are found in each segment except 

 the first three and the last. The receiving opening, the ciliated 

 nephrostome, is situated one segment anterior to the one contain- 

 ing its own yuphridium and nephridiopore. From the nephrostome 

 or funnel, currents flow into the ciliated neck which passes through 

 the anterior wall of the segment behind, then into a narrow tube 

 which coils three times and then opens into a wide glandular tube^ 

 which expels the waste at the external opening, the nephridiopore. 

 About half of the nephridiopores are situated on the ventral surface 

 in front and slightly laterad to the outer seta of the inner double 

 row; while the remainder of the excretory apertures are high up on 

 the side of the animal, dorsad to the row of dorsal seta bundles, at 

 irregular distances.^ 



Solid wastes pass out the anus and gaseous wastes through the 

 dorsal pores of the body wall, which are mid-dorsal, in the groove 

 between the segments. The first one is between segments ten and 

 eleven and opens into segment eleven. 



Reproductive System. (Figure 46.)— The earthworm is hermaph- 

 roditic (monoecious) with the gonads of both sexes, but does not 

 fertilize its own eggs. 



Female 



Internal Structures External Structures 



Ovaries, 13th somite. Oviducts opening at 14th somite. 



Two pairs of setninal receptacles. Openings to the seminal receptacles be- 



tween the 9th and loth; and the 

 loth and nth somites. 



^ In our description of the earthworm it will be noted that certain errors of most 

 textbooks have been corrected, particuhirly in treating of the calciferous glands, the 

 position of the nephridiopores, and the collecting vessels in the anterior somites. Such 

 corrections were inspired by the paper by Frank Smith, Certain differences between 

 text book earthworms and real earthworms. Trans. 111. Acad. Sc, vol. 17, pp. 78-83. 

 For systematic study of the Annelida, see Verrill, A. E., 1880, New England Annelida. 

 Trans. Conn. Acad. Sci., vol. 4. 



