136 PROFESSOR MARSHALL AND EDWARD J. RLES. 



of the two sides, are conspicuous features in his figures, and will be 

 referred to again further on. 



Duval's* description of the development of the head kidney and 

 its duct in the frog is illustrated by a series of useful figures, but 

 contains no new matter of importance. In all essential points he 

 agrees with Fiirbringer. 



Wichmannf also confirms Fiirbringer's account. 



Hoffmann]: adds a few details to the previous description. He 

 notes that the cells lining the nephrostomial tubes bear fiagella, and not 

 cilia as sometimes stated. Each cell bears a single flagellum, which 

 is considerably longer than the diameter of the tube in which it lies, 

 and is normally directed along the axis of the tube, with its free end 

 pointing inwards, i.e., towards the kidney and away from the peri- 

 toneal opening of the tube. 



The most recent paper on the development of the Amphibian 

 head kidney with which we are acquainted is a short note by Mr. 

 J. H. Kellogg,§ in which the following passage occurs : " The most 

 important point to be noticed is the formation of the so-called 

 ventral part of the gland. It has always been described, at least in 

 Amphibia, as being formed from that part of the duct immediately 



behind the last or most posterior nephrostome In 



Amblystoma, and also in the frog, this lower portion is formed from 

 the ventral side of the dorsal part of the pronephros and anterior to 

 the last nephrostome." Mr. Kellogg's description is perfectly correct, 

 but it is also in exact accordance with the accounts given by Fur- 

 bringer and Goette, the recognised authorities on the subject, and 

 not, as he supposes, at variance with these. 



2. The Early Development of the Head Kidney and its Duct. — We 

 have worked over these early stages carefully ; but inasmuch as 

 our results agree in almost all points with Fiirbringer's, we do not 

 propose to describe them in detail. 



* Duval, " Sur le Developpement de T Appareil Genito-Urinaire de la Grenouille. 

 D'e Partie — Le Rein Precurseur," Montpellier, 1882. 



t Wichmann, "Beitrage zur Kenntniss des Baues und der Entwicklung der 

 Nierenorgane der Batrachier," Bonn, 1884. 



J Hoffmann, " Zur Entwickelungsgeschichte der Urogenitalorgane bei den 

 Anamnia," " Zeitschrif t f iir wissenschaf tliche Zoologie," Bd. 44, 1886. 



§ Kellogg, [" Notes on the Pronephros of Amblystoma Punctatum," "Johns 

 Hopkins University Circulars," vol. ix., No. 80, Baltimore, April, 1890, p. 59. 



