WOLFFIAN DUCT AND BODY IN THE CHICK. 465 
step between them is not great.' It is merely necessary to 
suppose the division of the glomerulus (in fig. 24) into two 
parts, and a simultaneous development of certain folds from the 
Wolffian duct to form the tubules, and the original single 
tubule would have been transformed into a ventral primary 
and a dorsal secondary tubule. 
Further, as I have pointed out in another paper, the secon- 
dary tubule always arises in close proximity, apparently from 
a blastema continuous with a part of that from which the 
primary tubule arose. 
A modification of development is to be expected, because in 
those animals in which the mesonephros develops after hatching, 
it clearly comes gradually into use. The whole is not wanted 
at once, but with the increasing size of the larva, more tubules 
are wanted. ‘The first developed (primary) in Salamandra 
acquire a structure with which they can apparently perform 
their function when there is hardly a trace of the secondary 
tubules (Furbringer, loc. cit., fig. 26). 
' It will be observed that in this figure the tubule connecting the 
Wolffian duct and capsule is hardly developed. In all probability, this was 
on the analogy of the pronephros, the primitive state of things, the tubule, 
being a secondary differention of the duct near each glomerulus. 
?* Quart. Journ, Mier. Sci.,’ April, 1880. 
