hall: mesonephuos and mullerian duct in amphibia. 55 



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

 This I did throughout two somites iu my oldest specimen with the follow- 

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

 sum of the primary and secondary glomeruli, which points to the 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 nuniber of 

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

 but rather that some tertiary 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 

 assure 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 fact 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 secondar}', 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. 



Descripfioit of Talile 1 and Diagram 1. 



I wish now to call attention to Diagram 1 and Tai)le 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 tlie earlier stages the position of the units was deter- 

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

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

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

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

 uumbers-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 secondary units send 

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

 Triton tiiey do not. 



