42 T. H. BURLEND, 



tubule nearest the pronephric duct is very thin and in some cases 

 (at the posterior end of the pronephros and anterior end of the 

 mesonephros) still solid, it is necessary to make diag-rams of the kidney 

 of a number of embr3^os before I can hope to obtain an accurate 

 representation of the pronephros in these later embryos. 



Kidney on left side. 



Sections 4,12--4,14 passed through the 6tb spinal nerve. 



Sections 5,36 and 5,37 passed through the lOth spinal nerve. 



The front end of the pronephros (tubules) is cut through in 



section 4,20. Glomus begins at 4,20. 



VII { 1st tubule (degenerating) opens at 4,27—4,32 



/ 2û<i tubule has nephrostome at 4,34 and 4,35 



^ 3"l tubule 4,37 



IX { 4th tubule 4,44 and 4,45 



^. r ^ , , 1 / 4,50 and 4,51 



X ; oth tubule .......; ^32 and 4,63 



..T / . u , 1 / 4,65 to 4,68 



XI { 6th tubule I 4;,2 ^„^ '^^^3 



Behind this region the tubules appear to be undoubtedly meso- 

 nephric (see Textfig. K). 



Kidney on right side. 



Glomus begins 4,22 



Kidney tubules begin 4,23 



VII { 1st tubule has a nephrostome opening 4,27—4.29 



, , , at { 4,34 



VIII ^ 2UC1 tubule ^^^^ I 4 37 ^^ 4 39 



i , , (isolated) 4,45 \ 



IX { 3rd tubule ^J ^l^g / 



( 4.54 \ 



X { 4th tubule ^^^ 4^-e } 



VIII 



XI 



there are nephrostomes (mesonephric?) at 



4,64 

 4,69 

 4,73 

 5,1 etc. 



The body-segments in the above .embryo are numbered by 

 reference to the earlier embryos (see Textfig. L). 



