VIII 



SUBJECT INDEX 



MORPHOLOGICAL AND GENERAL SECTION 



ABDOMINAL PORES {OF FISHES) 



Or Fori abdominales, including a discus- 

 sion of the "genital pores" (Fori geni- 

 tales) with which they have been frequently 

 confused. 



The abdominal pores 



" Abdominal pores [as defined by Bles, E. J. 

 1898.1, p. 484] are the external apertures, usually 

 paired, found in many Anamnia and some Am- 

 niota in the cloacal region, affording a passage 

 of communication from the abdominal cavity 

 to the exterior. The integument surrounding 

 the pores externally is invariably ectodermic 

 in origin, usually proctodseal. Internally the 

 pores lead into the body cavity, or into passages 

 — the peritoneal canals — communicating with 

 the body-cavity." 



They occur in numerous genera in the Cy- 

 clostomes, Elasmobranchs, Dipnoi, and Teleo- 

 stomes, except in the Teleostei, where only two 

 families possess them. They are subject to 

 considerable variation in position and are often 

 absent in individuals of species in which they 

 normally occur. In other individuals they may 

 be open on one side and closed on the other. 

 In some species they open into the cloaca and 

 in others, directly to the exterior. These mi- 

 nute openings are often difficult to demon- 

 strate but, when present, they may generally 

 be disclosed by injecting the body-cavity with 

 mercury. 



The abdominal pores are considered to be 

 "excretory ducts" by Bles (E, J.. 1898.2, p. 

 243) who has made the interesting observation 

 that in those sharks in which open peritoneal 

 funnels persist and function throughout life, the 

 abdominal pores are- generally absent. (For a 

 further discussion of this subj ect, see below 

 " Urogenital system of Elasmobranchii " under 

 " Urogenital system.") 



Gegenbaur (C. 1870.1) beUeved that, in the 

 primitive vertebrates, the abdominal pores were 

 probably the sole efferent channels for the 

 sexual products. In contrast with this view, 

 Bles (E. J. 1898.1, p. 505) beheves that the 

 abdominal pores " never serve under normal 

 circumstances as genital ducts," this function 

 being performed by the true gonoducts or 

 where these have degenerated, as will be made 

 clear later, by the " genital pores." 



In the Teleostei, true abdominal pores occur 

 only in certain genera (Argentina, Coregonus, 

 and Salmo) of the Salmonidse (used in the older 

 sense), and, as was first pointed out by Hyrtl 

 (C. J. 1856.1, Add. 1849.1), in various species 

 of MoTTnyrus and in Gymnarchus niloHcus of the 

 Mormyridae. The abdominal pores exist in 

 both sexes.. 



The most illuminative and complete 

 •papers {in English) , on the abdominal and 

 genital pores, are those of -A-Bles, E. J. 

 1898.1, 1898.2. 



The most recent summaj^y in German is 

 that o/*Lickteig, A. 1913.1. 



The subject of abdominal and genital 

 pores in the Teleostei, is best treated by 

 •Weber, M. C. 1886.1. 



The confusion, among the older writers, 

 of abdominal and genital pores, especially 

 of Balfour (F. M. 1876.2, p. 35), which 

 was repeated by his pupil. Bridge (T. W. 

 1879.1), was first cleared by the remark of 

 Huxley (T. H. 1883.2, p. 137) that the 

 so-called abdominal pore of salmonoids 

 '* has nothing to do with the abdominal 

 pores of . . . [Ganoids and] Selachians." 

 This view was accepted by Gegenbaur 

 (0. 1885.1). The confusion was finally 

 cleared by the careful elucidation of •Weber 

 (M. C. 1886.1). 



The genital pores 



When the generative ducts (oviducts) dis- 

 appear, their external openings persist as the 

 genital pores. Through these openings the 

 sexual products are extruded. Except possi- 

 bly in the Cyclostomata, true " genital pores " 

 exist, as far as known, only in two families of 

 Teleosts, namely the Salmonidse and the An- 

 guillidee. As long ago pointed out by Rathke 

 (M. H. 1820.2), the oviduct in the eel has en- 

 tirely disappeared. Various stages in the 

 degeneration of the oviducts are found in the 

 Galaxiidae, Hyodontidae, Notopteridse, Osteo- 

 glossidse, and in Misgurnus, as has been shown 

 by Hyrtl (C. J. 1850.1, 1851.2) and by Mac- 

 Leod (J. 1881.3). In the Salmonidse, the ovi- 

 duct has practically disappeared. 



Abdominal pores and genital pores co-exist 

 in but one family of Teleosts, namely in the 

 female Salmonoid. 



In the Mormyridae, the only other family of 

 Teleosts possessing abdominal pores, the ovi- 

 ducts have not degenerated so that genital pores 

 are not present. 



Pores of the Cyclostomata 

 In this group, the genital products (eggs and 

 sperms) are discharged through a median pore 

 or a pair of pores. 



The exact morphological nature of these 

 pores, I. e., whether abdominal or genital pores, 

 remains in obscurity. Bles (E. J. 1898.2, p. 238) 

 says that there is " great probability that the 

 so-called abdominal pores of Cyclostomes are 

 genital ducts, morphologically as well as func- 

 tionally." Lickteig (p. 282), however, con- 

 siders them to be true abdominal pores, and 

 believes that it is only in this group that the 

 abdominal pores serve as channels for. the 

 sexual products. From d priori considerations, 

 this view is probably correct. 



1 Arranged under the 118 specific and technical headings herewith given. 



For fossil forms, natural history, occurrence, taxonomy, etc., matters relating to .specific fishes or groups 

 of fishes, see in the Systematic Section. 



