ANN U LATA. 255 



preceding anatomists, call the ovaries, roundish corpuscles with a 

 reticulate surface, presenting in that structure an unmistakable resem- 

 blance to the parts regarded by Weber as the ova of the medicinal 

 leech, and by Wagner as those of the //. vulgaris. 



The uterus, d, has a glandular lining membrane, a muscular tunic 

 of longitudinal and transverse fibres, and a cellular 

 ^y^Yy outer coat. It opens by a short duct, or vagina, on 



^^ ' the twenty-ninth ring. It contains a collection of 

 eggs, with chorion. Brandt remarked, in a much 

 distended uterus, although the major part of its con- 

 tents had been already evacuated, a delicate mem- 

 brane like the chorion of an ovum, in which were 

 many small yellowish corpuscles, very like the above 

 described ova, which led him to suppose that that 

 Leech. delicate membrane was the already developed inner- 



most cocoon-skin. 

 In the naids the orifices of the male and female organs are in two 

 pairs, situated about the anterior third of the body. In the Nais 

 proboscidia the ovarium is included by the substance of the testis. 

 Two cfEca extend inwards, at the breeding season, from the two 

 anterior generative pores, which are then found filled with sperma- 

 tozoa grouped into fasciculi, and probably received from another 

 individual in co'itii. The ova are carried out by long convoluted 

 oviducts. 



In the earth-worm the external characters of the generative orjrans 

 may be clearly seen in Hunter's dissections. We perceive here, that 

 tlie generative apparatus is more concentrated in the earth-worm than 

 in the leech, and more individualised than in any other animal of the 

 anellidous class. The three pairs of small opaque organs, which 

 Hunter regarded as testes, may possibly be only " spermathecoe," 

 like the anterior pair in the naids. They are laden with spermatoza 

 during the breeding-time. The germinal vesicles and developing ova 

 are found in the larger gray-coloured caica ; each of which sends out 

 a distinct short oviduct, and these combine into a common oviduct on 

 each side, opening behind the orifices leading from the testes or sper- 

 niathecK. If a section of one of these ovarian sacs is made, it is 

 found filled with a spongy matter in the centre, and the ova are 

 situated in this. The common oviduct from each lateral series of 

 ovaria terminates in the fissure upon the sixteenth segment, about 

 one-third from the head. It is interesting to note Iiere, that tlie con- 

 dition and function of the oviduct in the earth-worm is analogous to 

 the arrangement of the generative parts in plants. In plants, the 

 part answering to the oviduct is a distinct canal, communicating with 



