332 MOLLUSCA 



The always unpaired sexual origans in some forms ^Cvelohranchs and many 

 Zvi,'obranehsi emplv into ihe nephridia and possil.ly iho others utili/.e the rudi- 

 nieMits of the ri-ht kidnev. Idie sexual openin.L,' is almost always on the n-ht 

 side, beside the anus or in front of it on the head. Its position may he reeo^- 

 ni;:ed in males and in hermaphroditie speeies hy the ,L,'roo\ed dermal fold, the 

 penis ^tiL,'. 5i8, /''■). (.leeasionally this is separated from the -^jenital pore, 

 but is connVeted with it hy a ciliaieil t;roo\e. The sexual organs are \ery 

 variable in sirueture. They show two extremes. c1n the one hand are com- 

 pletely dieveious speeies, on the otlier there may be complete hermaphroditism 



Fie.. 330. — .\natoniv i'( llilix pomal'hi. Ihe roof of llie pulmonary sae cut at Ihe 

 left side anil turned to Ihe ris^hl; the ]H'rieanliuni and \iseei-al sae opened am! tlu- 

 viscera separateil. ./. aiui^; <\ eolumeUar nuisek-; i/. intestine; e;. alhunu-n ,L;lanii; 

 /, tinger-lorni inland; //, lla^elluni; /«, fool; i,-, cerebral t;-ani;hon; /;, heart, /, liver; III. 

 \\m\x; III, stoniarh; 11. nephridiuni; ;/', its o|ieninL,'; />. |ienis; />v, ilail sae; -■■, reeepl;>eulun\ 

 seminis; ,v, phar\nx; ,v/', sali\;ir\' L^l.iml; li . lUerus; ;', \.i,L:;in;\ ,;'(/, \. is deferens; ^, her- 

 maphroelile L;;on;id. 



(manv Teetibranchs, ]^teropod;i), in which (he male and female origans arc 

 united throughout their extent. Intermedi;itc stashes occur, tluit of the pul- 

 nionates is shown in Iil;. 3 io- 



The lerreNlri;il siKiils l;iv their larL;e touidi-shelh'd cl;l;s in d:imp earth; in 

 the aquatic forms the eL;y;s are hiid in ni;isses, usikiIIv !.;el;ilinous, each cl;,l; with 

 a layer of albuniiai ;ind ;i lirm shell. C)ce;ision;illv there is ;i kind of nest, 

 as is the case with luiiHrini whiidi c;\rries the mass of cl^l^s, altiicheil to the fool, 

 about with il. .V lew ;;asleropods arc \i\iparous. 



