hall: meso^'ephros and ml'llerian duct in amphibia. 55 



possess outer tubules or whether some of the tertiary also possess them. 

 This I dill throughout two somites ia my oldest specimen witli the follow- 

 ing results : The number of outer funnels was somewhat less tluin the 

 sum of the primary and secondary glomeruli, which points to tlie con- 

 clusion that only primary and secondary units possess outer funnels at 

 this stage, — and possibly the same is true in the adult.^ The fact that 

 the sum of the primary and secondary glomeruli exceeds the number of 

 outer funnels does not necessarily mean that some lacked outer tubules, 

 but rather that some tertiai'y glomeruli were included in the enumera- 

 tion. In fact, before comparing the numbers, I had marked some as 

 possibly belonging to the tertiary set. The position of the glomeruli of 

 the different sets is so variable at this stage that I was compelled to 

 plot the openings of the collecting trunks into the duct in order to 

 assui'e myself that what I took to be secondary glomeruli were not 

 merely primary ones which had shifted their position dorsad. The 

 number of openings found differed by only two from the number of 

 those which I had considered as primary. 



The plotting also brought out the fiict that, at this late stage, there 

 has been no change in the relative number of units in the different sets. 

 There is still one secondary for each primary (in the region of the secon- 

 dary), one tertiary for each secondary, etc. Six or seven sets are present. 

 All are functional except the two dorsal sets, of which the most dorsal 

 consists of small, spherical, darkly staining blastulae. 



Description of Table 1 and Diagram 1. 



I wish now to call attention to Diagram 1 and Table 1, pages .56, 

 57. In the diagram I have plotted for the right side of the body in 

 twenty-one individuals the position of the mesonephric units, the extent 

 of the germ-cell mass, and the position of the opening of the duct into 

 the cloaca. In the earlier stages the position of the units was deter- 

 mined by the point of greatest diameter in the blastula ; in tlie later 

 ones the glomeruli were taken as representing the units. In the case of 

 the secondary, tertiary, etc., units, only the most anterior one is indi- 

 cated. In Table 1 (page 57) I have translated the plotted units into 

 numbers-per-somite for more ready comparison. By examining the dia- 

 gram and table, the following questions can be answered : — 



(1) Do any units degenerate and disappear] 



1 Fiirbringer ('78) states that in Salamandra maculosa the secomlarv units send 

 outer tubules to the peritoneum. Hoffmann ('86), on the other hand, states that in 

 Triton tliey do not. 



