SUBJECT INDEX — MORPHOLOGICAL SECTION 



607 



functioning only in larval vertebrates. For 

 possible exceptions to this statement among 

 Teleosts, see below under " Persistence of 

 pronephros." 



As pointed out by Sedgwick (1881.1) the 

 pronephros is greatly reduced or non-func- 

 tional in meroblastic vertebrates. 



Origin of pronephric duct. Various con- 

 clusions have been held concerning the origin 

 of the pronephric (called also archinephric and 

 segmental) duct. In Elasmobranchs, this was 

 described by van Wijhe, Beard, Ruckert, and 

 Gregory, as arising by the spUtting off of a longi- 

 tudinal ridge-like projection from the ectoderm. 

 More recently Rabl and Bates have maintained 

 that the anlage of the duct is a direct outgrowth 

 of the pronephros and therefore mesodermal 

 in origin. 



Discussions of the origin of the pro- 

 nephric duct in Elasmobranchs. *Bates, 

 G. A. 1914.1; Beard, J. 1888.5; Gregory, 

 E. B,. 1897.1; Haddon, A. C. 1886.1; 

 •Rabl, C. 1896.1; •Riickert, J. 1888.2, 

 1889.2; Wijhe, J. W. 1886.1, 1888.1,.2, 

 1898.1. 



Similar conflicting views have been held 

 as to the origin of the pronephric duct in 

 Teleosts. Brook, G. 1888.1; Oellacher, J. 

 1872.1, .2. 



Origin of Miillerian duct. In selachians 

 as first discovered by Semper (Semper, C. G. 

 1874.1) and also independently observed by 

 Balfour (Balfour, F. M. 1876.2, p. 20), the 

 archinephric duct by a longitudinal splitting 

 from before backward forms a dorsal duct 

 (Wolffian, Leydig's or mesonephric duct) and 

 a ventral duct to which Balfour limited the 

 term, Mullerian duct. In males, the splitting 

 is more partial and in general only parts of the 

 Miillerian duct persist. 



It is now generally accepted that, although 

 differing in development, the Mullerian duct 

 in all higher groups of vertebrates becomes the 

 functional oviduct and is generally considered 

 homologous throughout the vertebrate series. 

 In the Teleost, however, the oviducts seem to 

 be mainly ovarian in origin. 



BaKour, however, believed that in the 

 Teleosts also, the oviducts are modified Miil- 

 lerian ducts and this view has at times gained 

 some acceptance. This master is further dis- 

 cussed below. 



For full discussions of the origin of the 

 Miillerian duct in Selachians, see Holz- 

 bach, E. 1909.1; Rabl, C. 1896.1; 



Riickert, J. 1888.2; Wijhe, J. W. 1888.1- 

 1889.1. 



Jn male Dipnoans, Miillerian duds 

 have disappeared in adults of Lepidosiren 

 but persist in Protopterus. Kerr, J. G. 

 1901.1. 



Mullerian ducts persist in adult males of 

 Chimcera. Hyrtl, C. J. 1854.3. 



Matthews records the presence {terato- 

 logicdi) of a fully developed Miillerian duct 

 on the left side of a male of Raja clavata. 

 Matthews, J. D. 1885.1. 



References to the Teleostean oviduct will 

 be found below under Phylogeny of the 

 Teleostean oviduct. 



Oplsthonephros 

 inclusive of the mesonephros 



A recent term, " opisthonephros," is de- 

 fined by Prof. Kerr (Text-book, p. 221) as 

 follows: " In many of the lower vertebrates 

 there is no separation between mesonephros 

 and metanephroB, the two forming a contmuous 



structure which acts' as the functional kidney. 

 Such a type of renal organ, consisting of the 

 series of tubules corresponding to mesonephros 

 together with metanephros, may convemently 

 be termed the opisthonephros." _ M 



The opisthonephros forms the functional 

 kidney in adults of all anamniotic vertebrates. 



MORPHOLOGY BY GROUPS 



Urinogenital system of 



Cephalochordata 



In Amphioxus the chief renal organs 

 consist of many (about 100) _ pairs of 

 minute nephridia discovered independ- 

 ently by Boveri and by Weiss. 



Structure of the excretory organs in 

 Amphioxus. •Boveri, T. 1890.1-1904.1; 

 •Goodrich, E. S. 1902.1, .2, 1903.1, 1909.1; 

 MilUer, W. 1875.1; Rolph, W., 1875.2; 

 Weiss, F. E. Add. 1890.1. 



Structure of the reproductive organs. 

 Legros, R. 1896.1, 1909.1; Neikert, L. & 

 Leiber, A. 1903.1; •Zarnik, B. 1904.1, 

 1911.1. 



TTrinogenital system of 

 Cyclostamata 



Reproductive Organs 



Thete is no connection between the excre- 

 tory and reproductive organs in the Cyclosto- 

 mata. The genital products (eggs and sperms) 

 are liberated into the coelom and pass out 

 through the genital pores. 



Structure of reproductive organs in 

 Bdellostoma. Cunningham, J. T. 1886.2. 



Structure of reproductive organs in 

 Myxine. Cunningham, J. T. 1887.2; 

 Schreiner, K. E. 1904.1, .2; Weber, M. C. 

 1887.2,.3. 



The reproductive organ of Myxine is said 

 to possess the combined structure of^ ovary 

 and testis (ovotestis) and to function as 

 both, i. e., as a protandric hermaphrodite. 

 For a further discussion, see under Her- 

 maphroditism. 



MYXINOIDES 

 Excretory Organs 



The excretory system of the Myxinoids is 

 the most primitive in craniates. The nephrid- 

 ial tubules develop as a continuous series, 

 the intermediate tubules later degenerating 

 (anterior remaining as pronephros) when the 

 posterior part of the organ (mesonephros) , ex- 

 tending over between twenty and thirty somites 

 each with its tubule and Malphigian body, be- 

 comes the functional organ. Some workers 

 (Semon, R. 1897.1) have considered the func- 

 tional kidney to be a pronephros, but this view 

 is now generally considered to be in error. 



Structure and development of the excre- 

 tory organs in Myxine. Joseph, H. 1905.1; 

 Kirkaldy, J. W. 1894.1; Maas, O. 



1897.2; MuUer, W. 1873.2; Semon, R. 

 W. 1897.1, .2; Semon, R. W. & Spengel, 

 J. W. 1897.1; Spengel, J. W. 1897.1, .2. 



Structure and development in Bdellos- 

 toma. Dean, B. 1899.6; Felix, W. 1897.2; 

 •Price, G. C. 1897.1-1910.1; Weldon, 

 W. F. 1884.2. 



A recent paper by •J. L. Conel on 

 " The urinogenital system of Myxinoids " 

 appears in the Joum. Morphol., 1917, vol. 

 29, pp. 75-138, 12 pis. 



