Field. — Pronephros in Amphibia. 



PLATE V. 



Fig. 42. A portion of a cross section through the anterior trunk region of a larva 

 of Bufo, belonging to Stage V. The Figure shows the pronephros 

 in the region of the first nephrostome. X 110. 



Fig. 43. A section through the rudiment of the duct near its hinder tip, from an 

 embryo of Bufo belonging to Stage IV. X 500. Zeiss apochr. 

 4 mm. Oc. B. 



Fig. 44. A portion of a cross section through the anterior trunk region of an 

 embryo of Amblystoma belonging to Stage III. The section shows 

 the pronephric thickening in the region of its greatest development. 

 X 65. 



Fig. 45. A portion of a cross section through the anterior trunk region of an em- 

 bryo of Rana belonging to Stage IV. The section shows the pro- 

 nephric pouch in the region of the second nephrostome. X 110. 



Fig. 46. An embryonic blood corpuscle occurring in the glomus of a larva of 

 Bufo belonging to Stage V. X 955. 



