EKl.-l'MSIIKS. 



lOM) 



abovc'-iiiciitiiiiied folds of ndiiiosi' uieiubraiR', tln" imli'IiI 

 be^iiiiiiiijU' fartln'i- forward than the left, but not ex- 

 tending;' so far back. 'I'lu; structure and significance; 

 of these organs, especially in our conuiion Mel, lias 

 long l)eeu an obscure ciuestion, which was not eluci- 

 dated until recent times. 



{•"roui tlie preceding pages (p. 829) we know that 

 the Salinonoid family and sonic other fishes, among 

 them tlic faiiiih' of the Eels, are destitute of oviducts, 

 at least closed ones, such as appear in the remaining 

 Teleosts, and that the eggs of these fishes fall, wdien 

 ripe, loose into the abdominal cavit\', wliencc they are 

 expressed tlirougli a more or less deNclopcnl peritoneal 

 canal on each side, opening into the genital ijoix' just 

 behind the vent or into the urogenital aperture com- 

 uioii to the genitals and the urinary bladd(n-. The 

 testes, on the otlier hand, are furnished, e\en in tlu' 

 Eels, with efferent ducts (rasa defi'ri'iifia), which have 



hand, they occupy as caudo-abdoiniiial cavities the same 

 relation to the skeleton as the abdominal cavity proper. 

 The peritoneal fold in which tlu; intestine is sus])eiided 

 (mefievfcriKm) crosses from tiic intestine to the urinary 

 bladder, which lies behind the rectum — leaving in the 

 females a triangular opening (peritoneal canal) between 

 tlie lowest part of the rrclmii and the neck of the 

 bladder- and is continued backwards in the middle 

 of the ha'iiial caiiiil (or a little ol)lii|ncly). It thus forms 

 n. ])artition wall between tlu' two eaudo-abdoiuinal ca- 

 vities, susjKMided from a continuation of the peritoneum 

 proi)er, which lines tlui walls of these cavities and di- 

 vides them from tiic superposed prolongations of the 

 kidneys (caudal kidnexs). The most striking peculiarity 

 ill the generative organs of the common Eel is, how- 

 ever, the duplication of the parts contained in the 

 caiido-abdominal cavities, each organ consisting there 

 of two blades running side by side. 



.-<S.»£<qr' = 



.JiJ.'-*^^ 



Fig. 273. Ptprtions of the testes in AiiguiUa vulgan's. A, alHlominiil cavity (posturitjr part) and Laiulu-abiloiiiiiial cafity, opened aud wid] 

 the walls folded back to show the enclosed organs; natural size; after Brock. B, a portion of the young testes, at an early stage of deve- 

 lopment, in an Eel 23 cm. Inn.e, taken at Trollhiittan in 1848; magn. about 8 diam., to show how the testicular lobes (t) originate in a thin 



and transparent mesorchial fold (at first of uniform breadth) of the peritoneum. 



/•!, left. Ill, right testicle in the abdominal cavity; tsc, left, tdc. riglit testicle in the cando-abdominal cavity; vds, left, vdd, right testicular 



duct (viis deferens); vs, seminal vesicle; vu, urinary bladder; ra, abdominal, re, oaudo-abdoniinal divisions of the kidneys; ura, abdoininal. 



lire, caudo-abdominnl urethra; ;•, rectum, detached and laid to the left; vcd, vena cava dextra; cl, cloaca {anus). 



their common aperture, as usual, in the anterior wall 

 of the neck of the urinary bladder. Characteristic oi 

 the majority of the Enchelymorph genera, liut most 

 developed in our common Eel, are two backward pro- 

 longations of the abdominal cavity and the continua- 

 tions in these cavities of the generative organs, one 

 below each side of the caudal (post-anal) prolongations 

 of the kidneys. We have indeed seen a similar pecu- 

 liarity in the Flounders, though the secondary abdo- 

 minal cavities are there situated outside the ha'inal 

 canal (see above, pi). ?)70 etc.). Here, on the other 



The ovaries have the appearance of frilled bands; 

 but their inner (median) side is smooth, and the ap- 

 pearance of frills is caused by elevated, transverse (ver- 

 tical), simple or double, foliate lobules (ovarial lamella', 

 in which the eggs are developed) on the outer (lateral) 

 side, though so arranged that in the caudo-abdorainal 

 part of the ovary the inner blade has these lobules on 

 its inner side, and turns its smooth side outwards, to 

 face the outer blade of the .same ovary. The testes, on 

 the other hand, so long as their real nature was un- 

 known, bore the name, conferred on them for their 



