370 s. tïATTA : 



segments and are eut off from the scleromyotome in 4 segments. 

 In Stage iii, the separation of the Anlage from the myotome 

 goes as far backwards as the sixteenth or seventeenth segment. 



8. The anteriormost Anlage is found in the hind part of the 

 fourth somite and is the first to arise ; the second follows it, and 

 so forth. 



9. The Anlagen in each somite are secondarily united with 

 one another by the solid cellular cord which is budded out of 

 the anterior and posterior rims of the Anlagen themselves ; thus 

 the collecting duct {Saiiiinelrolir in the sense of KÜckert) is estab- 

 lished. This j^rocess is originally to be looked upon as the 

 com in a; to2;ether of the ends of the tubules. 



10. The canalization of the collecting duct begins within each 

 Anlage and proceeds, generally speaking, posteriorly, until the 

 Anlagen in front and back are put in free communication. 



11. Each Anlage grows dorso-laterally and acquires a tubular 

 form. The collecting duct is shifted gradually in a dorso-median 

 direction ; finally it comes to lie between the myotome, the 

 mesentery, and the chorda dorsalis. 



12. The tubules open in the coelomic cavity at the lateral 

 angle of the dorsal corner of that cavity. 



13. In the somites posterior to the ninth, the tubules are, 

 during Stage iii, cut off also from the lateral plate and establish 

 a long duct running, on each side, along the dorsal aspect of 

 the lateral plate where originally the tubules opened. Tliis is 

 the segmental duct ; the tubules and the coUectino; duct in the 

 somites anterior to this constitute the glandular part of the 

 pronephros. 



14. The glandular part, or the pronephros proper comprises 

 six somites, from the fourth to the ninth. The maxinuim number 



