d/4 S. H ATTA : 



The difference is, that the tubules in the posterior region are 

 soon cut off from tlie lateral plate and become the duct. 



2Ö. Between the epiblast on one hand, and the Anlage or the 

 duct on the other, there exists always a space, and the duct 

 has no connection with tlie epiblast except at its posteriormost 

 end where the epiblastic cells might, as judged from the mitotic 

 figures, contribute to the formation of the duct. 



26. In the somites posterior to about the twentieth somite, 

 tlie Anlage of the duct is represented by a few cells in each 

 segment probably detached from the dorso-lateral angle of the 

 nephrotome. These cells multiply and are transformed into 

 the segmental duct in the posterior part. 



27. In Stage ii, the Anlagen of the segmental duct are cut 

 off from the mother layer in a few somites ; in Stage in, the 

 duct is formed as far as about the eighteenth somite, while in 

 Stage IV, it breaks out into the cloacal cavity. The cloacal 

 opening of the segmental duct is found at a point where the 

 hypoblastic cloacal wall is reflected into the epiblast, these two 

 layers forming a diverticulum on either side. 



28. In stage iv, the primitive genital cells become apparent 

 in the nephrotomes of the posterior 10 or more somites ; they 

 can not be discriminated from other mesoblastic cells in the 

 next advanced Stage. 



29. The blood-vessels, which specially supply the pronephros, 

 acquire definite form in comparatively later stages, viz., at about 

 Stage V. The dorsal aorta pours out the blood into two pairs of the 

 blind vessicles, which are formed by the folding of the parietal 

 peritoneum and are found between the first and second pairs, 

 and between the second and third pairs, of the persistent tubules 



