GROWTH OF EGGS AND EGG-STRINGS IN NEPHELIS. 191 



alcohol (ca. one hour), and examined in a mixture of equal 

 parts of glycerine and potassic acetate, or in dilute 

 glycerine. 



Such preparations may sometimes in a few days become 

 dark, but they can be again clarified by a fresh supply of 

 the mixture or the dilute glycerine. Eggs thus hardened 

 can be examined in any desired position by carefully rolling 

 them over under the cover glass, beneath which there must 

 be a hair or a piece of paper to avoid hard pressure. 



Specimens can be coloured with Beale's carmine after 

 hardening in absolute alcohol, but these show no better than 

 uncoloured ones. 



I. Reproductive Organs. 



I must here express my deep regret that I have not been 

 able to consult a memoir of M. Robin (No. 1), in which he 

 has described the sexual organs of Nephelis. I have also 

 been unable to obtain two memoirs of an earlier date, by F. 

 Miiller (No. 2) and Leydig (No. 3). 



The form and structure of the male organs have been for 

 a long time tolerably well known ; the same cannot be said, 

 I believe, of the female organs. I shall therefore first define 

 briefly the position of the genital orifices, and then pass to a 

 more detailed account of the sexual organs, limiting myself 

 in the case of the male organ to such remarks as the context 

 seems to require. 



The male organ opens externally in front of the female 

 organ, in the median ventral line, as is always the case in 

 all hermaphroditic Hirudinea. The male orifice (?«. o., fig. 1, 

 PI. XVI) is situated in the 86th ring, and the female orifice 

 (/. 0., fig. 1) between the 38th and the 39th ring, the entire 

 leech being composed of 106 rings. The former is compara- 

 tively large and prominent, and its edge is thrown into radial 

 rugse. The latter is hardly perceptible, except in hardened 

 specimens, being a simple minute pore in the interannular 

 line. 



The Male Organ. — The testicular sacs {t., fig. 1), begin- 

 ning in the plane of the 71st — T3rd ring, about opposite the 

 junction of the gastric portion with the yellow intestinal 

 division of the alimentary canal, extend backward to near 

 the end of the body. Their form and arrangement agrees 

 perfectly with the European Nephelis. They are spherical 

 bodies arranged compactly together, two to three broad, in 

 two elongated masses, disposed on each side of the nerve- 

 chain. They vary somewhat in size, but not exceeding 

 1 mm. in diameter during the winter period of inactivity. 



