14 WILLIAM MORTON WHEELER, 



Letztere bildeten sich aus je einer central liegenden Anlagezelle her- 

 vor und vergrösserteu sich rasch auf Kosten der umliegenden, den 

 Follikel erfüllenden Zellen, welche unter bedeutender Abflachung gegen 

 die bindegewebige Wand des Follikels gedrängt wurden." In larvœ 

 65 mm long the ovary and testis could be readily distinguished from 

 each other, although the latter contained as yet no spermatozoa. 



FüRBRiNGER (1878) has little to say concerning the reproductive 

 organs and his statement on the posterior openings of the pronephric 

 ducts (ureters) is peculiar. He says (p. 43): "Später münden die 

 primären Urnierengänge gemeinschaftlich in den Abdominalporus aus." 

 Obviously he means the urinogenital papilla, into which both the ab- 

 dominal pores and the pronephric ducts, or ureters, open. 



Schneider (1879, p. 102) gives the following description of the 

 termination of the ducts, etc. : "Die WoLFP'schen Gänge haben sich 

 an ihrem Hinterende bei Fetromyzon zu einem unpaaren Gange ver- 

 einigt und treten in einen penisartigen, von der Rückenwand des 

 Mastdarmes vorspringenden Zapfen. Der unpaare Gang besitzt jeder- 

 seits eine Oetihung, in welche ein enger, von dem Hinterende des 

 Peritoneum gebildeter Gang mündet. Dieser Peritouealgang, die 

 WoLFF'schen Gänge und der Mastdarm sind vom Bindegewebe zu 

 einer soliden Platte vereinigt, deren Aussenfläche der Afterflossen- 

 muskel aufsitzt." 



Scott (1880) describes the two pronephric ducts as opening at 

 first separately into the cloaca. Just before metamorphosis they unite 

 to form a short common canal. The cloacal orifice lengthens and 

 finally a portion of the cloaca is constricted oif to form the sinus 

 urinogenitalis , which acquires an opening of its own to the outside. 

 The wall of the sinus which Scott believes to be entodermal becomes 

 perforated at two points by the abdominal pores, thus establishing 

 communications between the body cavity and the sinus and providing 

 passages for the ova and spermatozoa. 



GoETTE (1891) was the first to trace the origin of the repro- 

 ductive organs in the embryo of Vetromyzon. He recognized them at 

 a very early stage (before his stage 7, corresponding to my stage 4). 

 At this time the mesoderm lateral to the myotomes consists of a 

 number of cells of varying size and filled with yolk granules. Most 

 of these cells multiply, but a few remain as conspicuously large elements 

 surrounded by smaller cells and embedded in the parietal mesoderm 

 just lateral to the region which subsequently becomes the pronephric 

 duct. At this stage the mesoderm has not yet separated at its outer 



