246 Openings in the Wall of the Body-cavity of Vertebrates. 



and (2) through stomata. The latter alone form a communication 

 between the body-cavity and the lymphatic system in the Saurii, and 

 Mammalia which have neither abdominal pores nor nephrostomes. 



2. If stomata should not be present in the Teleostei and certain 

 Eeptilia mentioned above, they would form the only exception to 

 the generalisation that the body-cavity of Vertebrates is never com- 

 pletely closed. 



3. The function of the abdominal pores is the same as that of the 

 nephrostomes, viz., the voiding of waste products from the body- 

 cavity. 



4. The body-cavity in Pisces and the lower Amphibia is to a great 

 extent an excretory organ. 



5. The bulk of the available evidence does not favour the view 

 that the abdominal pores represent a pair of segmental tubules. 



6. They seem to be simple perforations of the abdominal wall, and 

 in this case would not necessarily be homologous in the various 

 groups of Vertebrates. 



List of the principal Books and Papers referred to above.* 



J. Anderson, " On the Cloacal Bladders and on the Peritoneal Canals in Chelonia," 



' Linn. Soc. Journ.,' vol. 12, 1876, p. 434. 

 H. Gadow, " Remarks on the Cloaca and on the Copulatory Organs of the Amniota," 



' Phil. Trans./ B, vol. 178 (1887), pp. 5—37. 

 A. Giinther, " Description of Ceratodus," ' Phil. Trans.,' vol. 161 (1871), p. 549 ; 



" An Introduction to the Study of Fishes," 1880, p. 123. 

 J. Hyrtl, " Beitrage zur Morphologie der TJrogenital-Organe der Fische," 



' Denkschr. k. Akad. Wiss. Wien,' vol. 1, 1850, p. 391 ; Ueber den Zusammen- 



hang der G-eschlechts- und Ham-Werkzeuge bei den Ganoiden," ' Denkschr. k. 



Akad. Wiss. Wien.,' vol. 8, 1854, p. 65; " Anatoinische Mittheilungen ueber 



Mormyrus und G-ymnarchus," c Denkschr. k. Akad. Wiss. Wien,' vol. 12, 1856, 



p. 1. 



H. F. E. Jungersen, "Die Embryonalniere des Stors {Acipenser sturio)," ' Zool. 



Anz.,' Jhg. 16, p. 464; " Die Embryonalniere von Amia calva," ' Zool. Anz.,' 



Jhg. 17, 1894, p. 246. 

 Joh. Muller, " Ueber den Bau und die Grenzen der G-anoiden," 1846 ; " Fernere 



Bemerkungen iiber den Bau der Ganoiden," ' Sitz. Ber. Akad. Wiss. Berlin,' 



1846, p. 74. 



M. Nussbaum, "Zur Kenntniss der Merenorgane," ' Arch. f. Mikr. Anat.,' vol. 27, 

 p. 466, 1886. 



R. Owen, "Description of Lepidosiren annectens," 'Linn. Soc. Trans.,' vol. 18, 

 1841, p. 343. 



W. N. Parker, " On the Anatomy and Physiology of Protopterus annectens," 1 Roy. 



Irish Acad. Trans.,' vol. 30, 1892, p. 109. 

 F. Schweigger-Seidel and J. Dogiel, " Ueber die Peritonealhohle bei Froschen und 



ihren Zusammenhang mit dem Lymph-gefasssysteme." ' Ber. Sachs. G-es. 



Wiss. Leipzig,' vol. 18, p. 247, 1866. 



References already given in the text are not repeated here. 



