hall: mesonephkos and mullerian duct in amphibia. 



57 



Explanation of Diagram 1. 



Mesonephric units of Amblystoma plotted according to position in the somite. Individual 

 larvae denoted by the letters A to U, with their lengths in millimetres immediately be- 

 low. Somites 9 to 20 are numbered in the extreme right-hand and left-hand columns. 

 The units are represented by solid' circles or ovals, — i-irigs indicating indistinct funda- 

 ments, whose number is uncertain. Circles numbered 2, 3, 4, and b (L- U) represent 

 the most anterior of the secondary, tertiary, etc. units. The wavy lines indicate the ex- 

 tent of the germ-cell mass. Crosses (in individuals K-0) show the position of the most 

 posterior o^ the. functional units. The position of the opening of the Wolffian duct into 

 the cloaca is shown at the bottom of the diagram (somite 20). 



9 



B 



2 



C 



2 



D 



E 



F 



G 



H 



/ 

 1 



J 



K 



L 



il/ 



iV^ 







P 



Q 



R 



5- 



T 



U 



.5 



L-V 

 



B-U 



Probable 



Number 

 of Units. 



1 



10 



2 



2 



2 





2 



1 



2 



1 



1 



1 



1 





1 













1 





1.4 



.3 



"^ 



1 to 2 



11 



2 



2 



2 



2 



2 



2 



2 



2 



3 



3 



2 



1 



2 



1 



1 



3 



1 





2 



2 



2.2 



1.5 



o 



2 



12 



2 



2 



2 



3 



2 



3 



3 



2 



2 



2 



3 



4 



3 



1 



2 



3 



2 



1 



3 



4 



2.3 



2.6 



0) 

 be 



0) 



2 



13 



3 



2 



3 



2 



2 



3 



2 



2 



3 



3 



2 



2 



3 



4 



3 



4 



3 



3 



3 



4 



2.4 



3.1 



> 



< 



2 to 3 



14 







4 



3 



3 



3 



4 



3 



4 



4 



2 



3 



3 



4 



4 



4 



3 



4 



3 



4 3.5 



3.4 





3 to 4 



15 











3 



4 



3 



3 





3 



3 



3 



4 



4 



2 3 



4 



5 



5 



5 







3.6 



3 to 4 



16 

 17 























6 



6 



4 

 4 



6 

 5 



5 



7 



3 3 



4 5 



5 

 5 



5 

 5 



5 

 4 



6 



7 



c 



O 

 <*- 



c 



'o 

 o 



4.7 

 5.2 



4 to 5 

 5 















1 





18 



























5 



8 



5 



6 



6 



5 



5 



8 



0) 



be 



bt) 



6.0 



6 



19 

 20 



























6 

 4 



6 



6 



7 





6 



7 



7 

 5 



8 





> 



<5 



OJ 



> 

 < 



6.5 





Table 1. 



Showing the number of units to each somite. The individual larvae are designated by the 

 letters .S to U ; the somites, by the numbers (9 to 20) in the first column. 



