ANNULOSA. 



45 



The genus Malacobdella is sometimes regarded as belonging to the 

 Nemertida. The genus Histriobdella is of doubtful affinities, but is usu- 

 ally referred to the present order. 



(Moquin-Tandon, Monographic de la Famille des Hirudinees, 1846 ; Ley- 

 dig, Zur Anatomic von Piscicola geometrica, Zeitschr. fur Wiss. Zool., 1849 ; 

 Dorner, Ueber die Gattung Branchiobdella, Zeitschr. fur Wiss. Zool., 1865.) 



(Claparede, Becherches anatomiques sur les Oligochcetes, Geneva, 1862 ; 

 Lankester, On the Anatomy of the Earthworm, Journ. Micros. Sci., 1864, 

 1865 ; Eatzel, Beitrage zur anatomischen und systematischen Kenntniss der 

 Oligochceten, Zeitschr. fur Wiss. Zool., 1868.) 



Fig. 40. Oligochffita. A, Anterior portion of Tubifex rivulorum, enlarged : p, Pharynx ; 

 i i, Alimentary canal ; d d, Dorsal vessel ; h, One of the "hearts " or contractile dilatations 

 of the pseudohsemal vessels. B, Anterior portion of Lumbricus terrestris, laid open and en- 

 larged : o, Mouth ; p, Pharynx ; g, Gullet ; m, (Esophageal glands ; c, Proventriculus ; s, 

 Gizzard; i, Intestine; Ji, One of the "hearts," borne on the side of the dorsal vessel ; t, 

 Testes ; sp, Spcrmatheca>. (After Lankester.) 



