Wall of the Body-cavity of Vertebrates. 



233 



The greater part of the information on the openings from the 

 perivisceral cavity to the exterior in the Elasmobranchii is contained 

 in two papers ; one by Semper,* on the urogenital system of Plagio- 

 stomes, the other, by Bridge, on " Pori Abdominales of Vertebrata."f 

 Semper describes the persistence in certain Elasmobranchs of a 

 number of open segmental funnels on the peritoneal epithelium 

 leading into the Malpighian bodies of the mesonephros. Such funnels 

 occur in all Elasmobranch embryos, but usually close during develop- 

 ment. Semper gives lists of species with and without nephrostomes 

 when adult, and shows that their presence cannot be correlated with 

 the presence or absence of other organs, among which he did not, 

 however, refer to the abdominal pores. Bridge was the first to 

 examine a number of Elasmobranchs expressly to determine the 

 distribution of abdominal pores amongst the species of these fishes. 

 He states that it was " not clear that the presence or absence of the 

 pores can be correlated with structural variations in other organs." 

 I was led to compare Semper's and Bridge's accounts of the distribu- 

 tion of nephrostomes and abdominal pores, and it at once became 

 evident that their presence in Elasmobranchs was, to a certain extent, 

 reciprocal. A few discrepancies which appeared have been investi- 

 gated, and my results, although they agree in the main with Bridge's, 

 differ from his in one or two important cases. A detailed discussion 

 of these cases will appear elsewhere. 



The species which have come under my own observation are : — 

 Carcharias acutus, Ruppel, C. glaucus, L., Galeus canis, Bonap., 

 Zyycena malleus, Risso, Mustelus vulgaris, M. and H., M. Icevis, Risso, 

 Hexanchus griseus, Gm., Heptanchus cinereus, 6m., 8 cy Ilium canicula, 

 L., 8. stellare, L., Pristiurus melanostomus, Bonap., Gestracion pMUppz, 

 Lacep., Spinax niger, Bonap., Scymnus lichia, Cuv., Centrophorus 

 granulosus, Bl. Schn., Rhina squatina, L., Pristiophorus cirratus, 

 Lath., Pristis zysron, Blkr., Rhinchobatus djeddensis, Forsk., Rlnino- 

 batus granulatus, Cuv., Torpedo narce, Risso, Narcine brasiliensis, Olf., 

 Raja clavata, L., R. maculata, L., MyliobaMs maculata, Gray, and 

 My I. sp. 



Table I contains all the species for which there are data respecting 

 both nephrostomes and abdominal pores. It includes all the species 

 investigated by Semper, excepting Lamna glauca, M. and H., and 

 Temera hardwickii, Gray. In these two species the nephrostomes 

 close, and it may be expected that they will eventually be found to 

 possess abdominal pores. 



Table II is so arranged that the species with nephrostomes are 



* C. Semper, "Das Urogenitalsystem der Plagiostomen und seine Bedeutung 

 fur das der iibrigen Wirbelthiere," ' Arb. Zool.-zoot. Inst. Wurzburg,' vol. 2 (1875), 

 pp. 195—509. 



f < Journ. Anat. and Phys.,' vol. 14 (1879), pp. 81—100. 

 VOL. LXII. S 



