. The biology of the frog . d vessels with which the kid-ney is supplied. The ventral surface ofthe kidney is furnishedwith numerous ciliatedfunnels, the nephrostomes,whose expanded ends openinto the ccelom. At theirother end the nephrostomesempty into branches of therenal veins, and the ciliawith which they are linedbeat toward the upper endof these organs and thuscreate a current of lymphfrom the body cavity intothe blood. This relationof the nephrostomes is apeculiar one and occursonly in the Anura. Thelower Amphibia preservethe typical arrangement ofthese organs, as the nephro-stomes are c
. The biology of the frog . d vessels with which the kid-ney is supplied. The ventral surface ofthe kidney is furnishedwith numerous ciliatedfunnels, the nephrostomes,whose expanded ends openinto the ccelom. At theirother end the nephrostomesempty into branches of therenal veins, and the ciliawith which they are linedbeat toward the upper endof these organs and thuscreate a current of lymphfrom the body cavity intothe blood. This relationof the nephrostomes is apeculiar one and occursonly in the Anura. Thelower Amphibia preservethe typical arrangement ofthese organs, as the nephro-stomes are connected with the renal tubules. This condi-tion, as Marshall has found, occurs also in the early stagesof the life of the frog, but later the nephrostomes lose theiroriginal connection with the tubules and become unitedsecondarily with the renal veins. The kidney of the male frog stands in an intimate relationto the sexual organs. The vasa efferentia, or ducts whichconvey the spermatozoa from the testis, pass into the sub-. FlG. 54. — Diagram of a kidney show-ing the ureter and collecting , collecting tubules; L, longitudi-nal canal of Bidder; S, seminalvesicle; T\ testis; U, ureter; VE,vasa efferentia. THE EXCRETORY SYSTEM 205 stance of the kidney, and the spermatozoa are carried throughthis organ to the ureter, which thus serves also as a vasdeferens. Thevasa erTerentia areoriginally out-growths of thewalls of the Mal-pighian corpus-cles which be-come connectedwith the some species(R. escu lento)the Malpighianbodies, which giverise to these out-growths, still pre-serve their originalfunction, and dur-ing the period ofsexual activityspermatozoa maybe seen in themas well as alongthe whole lengthof the renal tu-bules which arisefrom them. Thevasa erTerentialead into a longi-tudinal canal {Bidder s canal) which runs near the medianedge of the kidney. In Ranafusca, according to Beissner, this canal is con-
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