33(5 
SErCtNDARY UreTER AND PRONEPHROS. 
aporturo, it may assume a liackwavd directioii, fusing witli tlie wall 
of the secretory sac ami opening at the extreme rear of the mantle- 
chamher, as in TcstdccUit, etc., while an intermediate stage leading 
to the highest development ot the ureter is seen in the formation in 
some Helices ot a more or less open channel, leading from the aperture 
of the backwardly directed primary ureter in the rear of the mantle- 
chamher to the pulmonaiy orifice ; this channel eventually becomes 
Kig. G’2t. Fig. 02.). Fig. 020. Fig. 027. Fig. 028. 
Diagrams illustrating the development of the Ureter in the Gastropoda (after Lang). 
r. kidney or renal organ ; /.«. primary ureter ; s.u. secondary ureter ; r. rectum ; f>.o, respira- 
tory orifice ; /i. heart, within its pericardium. 
Fig. 02 L — Portion of respiratory chamber with the e.vcretory renal orifice existing as a simple 
papillar opening, as in certain Planorbes, etc. 
Fig. 62.5. — Shows the elongation of the simple exxretory orifice into a long and definite duct, 
the Primary Ureter as in the Hasommatophora and certain Sireploneures, etc. 
Fig. 626. — The Primary Ureter is directed backwards and adherent to the kidney, opening at 
the back of the respiratory cavity, as in Tcstacciia, etc. 
Fig. 027. — Shows the formation of an open channel leading to the exterior from the renal 
opening in the rear of the chamber, as in certain Helices. 
Fig. 02S. — Shows the formation of the open channel into a definite duct, the .Secondary Ureter 
and its junction with the rectum, as in our most highly organized Helices, etc. 
clo.sed and forms a detiiiite duct, di.stingui.shod as the Secondary 
Ureter, the name applied to the differently directed tract in con- 
tinuation of the hackwardly directed primary ureter of the Testacelhv, 
hut following a different direction, parallel with and opening into or 
near the rectum, a-^ in Ariou, AmaUd, Umax, Yitr'ina, ITyalinia and 
the more highly developed Helices. 
The Pronephros (-/.o, hefore ; 
Fig. 620. — Embryo of Plnnorbis cornctis 
(L.), seen from the left side, X IHO (after Fob), 
showing the Pronephros or primitive kidney. 
/;/. pronephros or primitive kidney ; c.o. its 
external orifice ; in. mouth ; r. rectum ; n. 
nephridium or permanent kidney, also showing 
external orifice ; d.gl. digestive gland ; in. in. 
mantle margin ; e.gi. cerebral ganglion ; 
/>.gi. pedal gland. 
i'€</)/)r)s, kidney), Wolffian bodies or 
provisional renal organs, known also 
as Stiebel’s canals, are possessed 
by many embryonic mollusca and 
are es])ccially characteristic of the 
Trochospherc stage of larval life, 
as they atrophy and disappear 
before the close of the Veliger 
])hase of develoiunent. 
They arise by ectodermic in- 
vaginations in the anterior region 
of the body, behind the velnm, but 
considerably in advance of the later and permanent kidneys of adult 
