382 s. HATTA : 



alimentary canal extending tlirougli about the same space as llie 

 glandular part of the kidney. Each glomerulus is a diverliculum 



of the peritoneum, which generally becomes sacculated; " 



(p. 1^1). The statements l)y Goette confirm SiiirLEY's, and ray 

 results also agree witli theirs. However, this is not all of the 

 vascular system of the pronephros but represents a posterior 

 portion of it, the anterior part having disappeared entirely 

 (see p. 3G8). 



No previous writer on Petromyzon has described such early 

 stages as given above in the development of the pronephros, nor 

 has any one remarked the temporary existence of the i^ronephric 

 tubules in the branchial region as well as in the reoion of the 

 segmental duct, I will, therefore, extend the comparison over the 

 allied groups such as jMyxinoids and Amphioxus, and higher 

 Cran iota to verify the new facts. 



With reference to the development of the nephric organ in 

 Myxinoids, there is a great deal of information which we owe 

 to the unwearied labors of W. Müller, Bemon, Weldon, and 

 others^'. They had, however, no opportunity to observe the earliest 

 stage of the embryos. Recently our knowledge on this subject 

 has been greatly augmented by the new works of Price, Dean, 

 and Maas. 



Price ('97) worked out the early development of the prone- 

 phros observed in a few embryos at different stages of Bdellostoma 

 i<touti. According to him " the first indication of the system 

 occurs here in the eleventh segment (of spinal ganglion), and 

 consists of a simple thickening of the somatic layer of the coel- 



])I liave not seen tlie paper by J. Mullfr. 



