Bennet M. Allen : 85 
line, however, might show a primary metamerism, from which the above 
described condition was derived by further secondary splitting of the 
nephrogenous tissue. Hach nephrotome becomes vesicular to within a 
short distance of the peritoneum thus forming the primary Malpighian 
corpuscles. ‘The remaining portion of the nephrotome uniting it with 
the peritoneum becomes, in later stages, the peritoneal funnel or nephros- 
tome, while the uriniferous tubule arises as an outgrowth from the distal 
end of the nephrotome. The mesonephric peritoneal funnels are vestigial 
structures from the time of their origin. 
In later stages (C-7. 6 mm.), two sharply defined regions of the 
mesonephros may be distinguished from one another. In the anterior 
part of the sex-gland, only the primary Malpighian corpuscles are 
formed. Each is well developed, the glomerular invagination having 
already taken place. The 11th to 21st Malpighian corpuscles are con- 
nected with the peritoneum by peritoneal funnels (Plate I, Fig. 5), some 
of which are much better developed than others, there being great vari- 
ation among them. In the best developed among them, the end attached 
to the peritoneum flares open to form an actual funnel-like mouth, yet 
this opening is never continuous with that of the Malpighian corpuscles. 
The greater part of the peritoneal funnel is merely a cord of cells. In 
some cases even, it has lost its continuity with the capsule of Bowman. 
At this stage the first ten Malpighian corpuscles are without peritoneal 
funnels. 
Caudad of the 21st Malpighian corpuscle, each nephrotome shows two 
or three rudimentary vesicular enlargements. Each enlargement is des- 
tined to form a Malpighian corpuscle. The most ventral of these we 
shall consider as the primary Malpighian corpuscle. It is still rather 
broadly connected with the peritoneum. This place of union we shall 
consider as a rudimentary peritoneal funnel, although it has no flaring 
opening. 
In later stages, secondary and tertiary Malpighian corpuscles appear 
in the anterior region described above, thus making the total number per 
somite approximately equal to that in the posterior region. Roughly 
speaking, from nine to twelve Malpighian corpuscles in all, appear in 
each somite. 
Reference to Plate I, Fig. 1, will show certain of the points mentioned 
above. Furthermore, one can see an elongated mass of tissue that ex- 
tends from each peritoneal funnel dorso-mediad and which lies just lat- 
erad of the V. renalis revehens (vena cava). This we shall term the fun- 
nel-cord. They appear in both the anterior and posterior regions of the 
mesonephros as described above and are co-extensive with the sex-gland 
