524 MR. T. H. BURLEND ON THE UROGENITAL [Mar. 1, 



smooth surface. They are invested with peritoneum, which also 

 forms a ventral covering for the corresponding Mullerian duct, 

 sperm-duct and kidney lying adjacent. In transverse sections it 

 is possible to make out a number of efferent ducts passing into a 

 collecting duct, which gradually passes into the coiled sperm-duct, 

 and so the vasa efferentia and sperm-duct have the same relation 

 as in the adult. No kidney tubules intervene, and the lining of 

 the former (efferent ducts) imperceptibly passes into the lining 

 found in the latter. 



The anterior coiled end of each sperm-duct is, even at this 

 period, much coiled and of greater size than the testes ; at a level 

 a little behind the latter it is but little coiled and rather wider, 

 and then passes practically straight back along the outer border of 

 the kidney until this joins its fellow of the other side, at which 

 level it passes ventral to the now wide and deep kidney to fuse 

 with the other sperm-duct in the middle line. It should be 

 noticed that in its posterior region the sperm-duct is still of 

 uniform diameter, the later changes to produce the seminal 

 vesicle being not yet apparent; further, ducts pass off to the 

 sperm-duct at intervals along the whole length of the paired 

 portion of the kidney, with the possible exception of the first 

 one or two segments. Behind, the unpaired kidney is drained by 

 six ureters arising from either side, and opening separately, 

 though very close together, into the respective sperm-ducts just 

 before the latter fuse and open into the urogenital sinus. 



Urinary Organs, 



These consist of a posterior brownish unpaired portion re- 

 presenting the adult kidney, and two ribbon-like paired brownish 

 bands, extending forwards to a level immediately in front of the 

 testes, with regular segmentation, and short ducts passing into 

 the sperm-ducts as described above. With the exception of the 

 first one or two segments — which appear degenerate — the kidney 

 possesses numerous glomeruli, as may be ascertained by staining 

 and clearing in oil of cloves. Each segment of the kidney — and 

 the segmentation, especially anteriorly, is very noticeable — 

 apparently consists of much coiled tubules with two or three or 

 even more glomeruli in the dorsal region. From the position and 

 relations of the paired portions of the kidney, it is evident 

 that later they loose their glomeruli and give rise to the glands of 

 Leydig of the mature male adult. 



Urogenital Sinus. 



There is no trace of sperm-sacs, but the chamber formed by 

 the fusion of the two sperm-ducts widens, and receives the two 

 Mullerian ducts, which apparently pass in close together in the 

 ventral middle line about half-way along its length. The Mullerian 

 ducts are not in open connection, however, with the sinus, nor do 

 they ever become so. 



