INTERRELATIONS OF THE MESONEPHROS, ETC. 191 



side. The average diameter, 200 micra, is very large when 

 compared with those of the early embryos noted above. At 

 11.0 mm. there are sixty active glomeruli, at 24.0 mm. eighty 

 on each side, and in each case the average diameter has reached 

 325 micra, six times that of the glomeruli of the guinea pig. 

 At 95.0 mm. many active mesonephric glomeruli with the same 

 large diameter are present, and in the same specimen the kid- 

 ney also contains two or three rows of apparently fully active 

 glomeruli, wdth bulging epithelial plates. It seems certain that 

 in the pig, as pointed out by Weber, the activity of the meso- 

 nephros overlaps that of the metanephros, as is the case in birds, 

 reptiles, and the opossum. 



In the sheep the comparison of the size and number of the 

 mesonephric glomeruli is an even less accurate guide to their 

 relative activity than in the other mammals studied, because of 

 the peculiar type of structure which the anterior corpuscles 

 present. As 1 have recently shown, ^ the first twenty or thirty 

 corpuscles are without true glomeruli; the lower or caudal ones 

 are of the usual type. But as the number of irregular, atypical 

 corpuscles is approximately the same at all ages, their pres- 

 ence does not vitiate the count to any great extent. In a sheep 

 embryo of 6.6 mm. there are six active glomeruli on each side in 

 addition to the twenty or thirty atypical corpuscles, and their 

 average diameter is 150 micra; at 15.8 mm. there are fifty nor- 

 mal glomeruli, of 230 micra; and at 40.4 mm. again fifty on 

 each side, but with an increased diameter, 285 micra. In the 

 40.4 mm. embryo the kidney contains several active glomeruli 

 with an average diameter of 100 micra. 



The cat of 7.6 mm. has about twenty active glomeruli in each 

 organ, diameter 150 micra; at 15.0 mm. the number has in- 

 creased to twenty-six, and the diameter to 165 micra, but each 

 glomerulus is much more lobed. At 39.0 mm. there are thirty 

 glomeruli with an average diameter of 200 micra, and in this 

 same specimen the innermost renal glomeruli are develop- 

 ing epithelial plates. At 85.0 mm. the Wolffian body has dis- 



' Bremer, loc. cit., p. 3. 



