Mr. A. Hancock on the Anatomr/ of Oithona. 301 



EXPLANATION OF PLATES IX. ANT) X. 

 Plate IX. 



Fig. 1. Side view of Oithona nobilis : — a, penis partially exserted; b, oriflce 



leading to the female and androg\Tious parts. 

 i%, 2. Dorsal view of the same, the papdlae of one side being removed : — 



a, anal tube ; b, small orifice at the base of the same, supposed to 

 lead to a renal organ ; c, heart ; d, great eiferent or branchio -car- 

 diac vessel, raised above the general surface ; e, small efi"erent ves- 

 sels, likewise raised above the surface, leading from the papillae to 

 the same. 



Fig. 3. Two of the papillae enlarged : — a, small efferent vessel leading to the 

 great median tnink ; b, puckered, membranous fringe with efferent 

 vessel running up its margin. 



Fig. 4 . Upper view of the buccal organ : — a, anterior extremity leading to the 

 channel of the mouth ; b, gullet ; c, c, horny jaws ; d, d, muscles 

 for advancing the whole apparatus. 



Fig. 5. Side vievr of buccal organ: — a, anterior extremit}-; b, gullet; c, homy 

 jaw ; d, muscles for advancing the buccal organ. 



Fig. 6. Side view of the tongue : — a, anterior extremitj-. 



Fig. 7- Sahvarj- glands ; the buccal organ and all the viscera having been 

 removed : — a, oral opening ; b, walls of the channel leading to the 

 buccal organ ; c, c, salivary" glands ; d, d, ducts of the same pass- 

 ing into the wall of the channel of the mouth. 



Plate X. 



Fig. 1. General view of the %-iscera seen from above : — a, buccal organ ; 



b, gidlet ; c, stomach ; d, intestine ; e, e, hepatic ducts leading 

 from the great lateral hepatic channels within the skin ; /, one of 

 these channels laid open, exhibiting the canals from the papillae 

 opening into the same ; g, g, folUculated glandidar bodies in con- 

 nexion with the anterior jjortious of the great hepatic channels ; 

 h, gland-hke substance in connexion with the hepatic channels in 

 the skin ; t, some of these channels laid open ; j, a jwrtion of the 

 right sahvary gland ; k, penis ; /, testis ; m, ovar}- ; n, n, n', mu- 

 cous gland in connexion with the female channel ; o, o, j>eri- 

 carthfd cavity seen in section ; o', o', floor of the same ; p, ven- 

 tricle ; q, auricle ; q', portion of the same attached to the great 

 efferent vessel in the skin; r, r, the great efferent vessel seen 

 in section ; s, portal heart, opening through the floor of the peri- 

 cardium ; t, orifice supposed to be in connexion with a renal organ, 

 and opening externally by the side of the anal tube ; u, cerebral 

 ganghons. 



Fig. 2. Reproductive organs separated from the rest of the viscera and 

 spread out : — a, intromittent organ retracted ; b, testis ; c, vas de- 

 ferens ; d, duct leading from the testis to the oviduct ; e, ovary ; 

 /, duct leaving the same ; g, dilated portion of the oviduct ; 

 h, constricted portion of the same ; i, the point w here it receives 

 the duct from the testis ; j, spermatheca ; k, duct from the same 

 leading to the oviduct ; I, female channel leathng to external ori- 

 fice ; m, vagina or copidatorj- channel leatling from external orifice 

 to oviduct and spermatheca ; n, n, n', mucus-gland in connexion 

 with the female channel. 



Fig. 3. View of the heart, the pericardium being laid open : — a, ventricle ; 

 b, aorta, passing from the front of the same ; c, auricle ; d, great 

 median efferent or branchio-cardiac vessel laid open, showing its 



