240 MR HAROLD AXEL HAIG ON 



since no downgrowth has occurred from the convoluted tubule to form 

 the loop.* 

 (6) A deep zone, in which as yet connective tissue preponderates, and through 

 which course the branching tubes derived from the Wolffian diverticulum ; 

 these tubules possess wide lumina, and are lined by a clear cubical epi- 

 thelium. They represent the rudiments of the straight and collecting 

 tubules, those nearest the papilla becoming later on the ducts of Bellini ; 

 in the Phocidse, according to Chievitz,! many of the secondary and tertiary 

 branches of the Wolffian diverticulum disappear during development. 



The epithelium lining the convoluted tubules of the cortical zone is clear and 

 cubical, the nuclei staining but feebly with basic stains : the portion of the tubule, 

 however, which joins the ampulla is lined by smaller cells, the nuclei of which stain 

 deeply. The glomerulus in each Malpighian capsule is a well-developed capillary 

 tuft with already an indication of lobulation. 



Between the renal pyramids and supporting them there is a certain amount of 

 connective tissue (columns of Bertini) in which small blood-vessels are seen cut across 

 (capsular vessels of later stages). 



The adrenal bodies (PL XXII. fig. 2). — Kelatively speaking, the adrenals are much 

 smaller than one would expect at this phase of development, but their histogenetic 

 features are none the less instructive : each gland is enclosed in a capsule of connec- 

 tive tissue in which course branches of the adrenal artery and vein, whilst smaller 

 vessels (arterial) pass at right angles to the surface into the gland, being supported 

 by the fine septa which are given off from the inner aspect of the capsule. 



The substance of the adrenal is made up of the following parts : — 



(a) An outer zone, the commencing zona glomerulosa, composed of folded columns 



of small cuboidal cells. 



(b) A wide intermediate zone composed of anastomosing broad columns of large 



polyhedral cells : this is the developing zona fasciculata, amongst the 

 columns of which ramify the small vessels noted above as passing in from 

 the capsule. The cells of this zone are characterised by their small clear 

 nuclei, and their deeply-staining cytoplasm, which takes up eosin very 

 readily. 

 Throughout this zone are scattered small masses of rounded cells, with deeply- 

 staining nuclei, the sympathetic ganglion rudiments. These are aggregated 

 in larger masses in the central region of the gland, where they form the 

 anlage of the medulla. In the medullary region the blood-channels are 

 wide, and as yet are lined by a well-defined endothelium. 



* Chievitz (Archiv Anal. u. Embryol., Supplement, 1897) found HenLe's tubule present in an embryo of Phoca, 

 145 mm. in length. The present foetus is only 122 mm. in length, 

 t Op. cit. 



