2 WILLIAM MORTON WHEELER, 



The following study of the urinogenital organs of the lamprey 

 by means of modern methods and in the light of recent theories, 

 was suggested to me by my friend and teacher, Professor Theodor 

 BovERi. The work was completed under his kind supervision in the 

 laboratory of the Zoological-zootomical Institute at Würzburg during 

 the summer and autumn of 1893. Illness and pressure of other work 

 have unduly delayed publication, and have prevented what I deem of 

 equal importance, the expression of my gratitude to the brillant dis- 

 coverer of the excretory organs of Amphioxus for the time and ample 

 knowledge which he devoted to my work. 



The material studied consisted of the following stages: 



I. A lot of embryos of Petromyzon planeri from Naples. These 

 had been hardened in corrosive sublimate. They represent twelve 

 stages, in part showm in Goette's figures (1891, figs. 7—12, tab. 1), 

 and may be designated thus: 



Stage 1. (Goette's 4^^ period.) 



Stage 2. (Goette's 5^^ period.) 



Stage 3. (Goette's 6^^ period.) 



Stage 4. (Beginning of Goette's 7'^' period.) 



Stage 5. (Goette's fig. 11, tab. 1; 4 mm long.) 



Stages 6—10. (Between Goette's figs. 11 and 12; 5 — 6,5 mm 

 long.) 



Stage 11. (Goette's fig. 12; 7 mm; spiral valve forming.) 



Stage 12. (Somewhat older than the embryo represented in 

 Goette's fig. 12 ; about 7,25 mm long, with no yolk in the entoderm 

 cells. These larvse had begun to take food.) 



IL A lot consisting of four young Ammocœtes of Petromyzon 

 marinus dorsatus Wilder ^). These were given me by my friend. 

 Dr. H, P. Johnson, who received them from Prof. Gage of Ithaca, 

 N. Y. They were taken in Cayuga Lake. The labels bear the following 

 legends : 



Stage 13. Length 8 mm. "Picric alcohol. June 2b^^. Taken 

 from the nest." 



Stage 14. Length 9 mm. "Picric alcohol." 



Stage 15. Length 12 mm. "Killed in Perenyi's fluid. No 

 longer in the nest but in the bank along the stream, Cayuga Lake Inlet." 



1) See Gage & Meek (1886) and Gage (1893, p. 430). This is 

 regarded by Jordan & Evermann (1896, p. 10) as a synonym of 

 P. marinus unicolor De Kay. 



