ANNELIDA. 201 



round, whitish bodies ; these are the ovaria. The germs, there- 

 fore, which are formed in the ovarian corpuscles, escape through the 

 tortuous duct (h) into the uterus (), where they are detained for 

 some time prior to their ultimate expulsion from the body. The 

 exact nature of the uterine sacculus, as it is called, is imperfectly 

 understood : some regard it as a mere receptacle wherein the se- 

 minal fluid of the male is received and retained until the ova come 

 in contact with it as they pass out of the body, and thus are sub- 

 jected to its vivifying influence ; other physiologists believe that the 

 germs escape from the ovaria in a very immature condition, and sup- 

 pose that during their sojourn in this cavity they attain to more com- 

 plete developement before they are ripe for exclusion ; while some 

 writers go so far as to assert that leeches are strictly viviparous, in- 

 asmuch as living young have been detected in the interior of this 

 viscus : but all these suppositions are easily reconcileable with 

 each other ; there is no doubt that the seminal liquor is depo- 

 sited in this reservoir, during the copulation of two individuals, 

 neither would any one dispute that the ova are collected in the 

 same cavity before they are expelled from the body ; as to the 

 discussion whether the young are born alive or not, or, as it is ge- 

 nerally expressed, whether leeches are oviparous or viviparous, it is 

 in this case merely a question of words, for in a physiological point 

 of view it can make not the slightest difference whether the ova 

 are expelled as such, or whether, owing to their being retained by 

 accidental circumstances until they are hatched internally, the 

 young leeches make their appearance in a living state. 



(44.) Abranchia terricola. The second division of those Anne- 

 lidans which possess no external organs of respiration are easily dis- 

 tinguishable from the suctorial worms by the different construction 

 of their instruments of locomotion. They live in general beneath 

 the surface of the ground, either perforating the soil in all direc- 

 tions, as the Earthworms (Lumbrici), or burying themselves in the 

 mud upon the sea-shore, where many of them, called Naides, 

 (Nais, Lin.) live a semi-aquatic life. In conformity with such 

 habits, their entire structure is adapted to a subterranean existence, 

 and their bodies so organized as to enable them to burrow with 

 facility through the dense and unyielding materials in which they 

 are usually found. Whoever has attentively watched the opera- 

 tions of an earthworm when busied in burying itself in the earth, 

 must have been struck with the seeming disproportion between the 

 laborious employment in which it is perpetually engaged, and the 



