240 CLAVP OLE. [VoL. XIV. 
shows that the appendages on the segment bearing the genital 
opening have been more or less changed. Histologically, the 
condition of these modified appendages is given as being highly 
vascular, a description closely agreeing with the structure of 
the collophore in Anurida. On these grounds it is then possible 
that the collophore in Anurida is a relic of a former anterior 
opening for the reproductive organs, and that the cephalic 
elongation is a trace of the former duct. The exact present 
function of the collophore has long been a source of much 
conjecture, and still remains in doubt. . 
Fernald (90, p. 45) summarizes the views held as to the pos- 
sible present function of the ventral tube in the Collembola; 
two writers think it a genital organ, but its equal development 
in the male and female argues against this. Haase considers it 
a blood gill, a function he assigns to all the rest of the similar 
abdominal appendages found in the Symphyla, while it is said 
also to be a gland for the secretion of an adhesive mixture. 
Any of these functions may have been acquired since its origi- 
nal function was lost, but the evidence given above and its 
position on the fourth body segment — the same as that of 
symphyloid genital opening — give probability at least to the 
view here advanced of its primitive function. Kenyon ('95) gives 
a table of the appendages and their homologies in the various 
groups of arthropods, in which he considers the fourth segment 
of the Symphyla as the homologue of the third in hexapods, 
but upon what basis is not clear. Haase, Wheeler, and Grassi 
agree in thinking the homology of the fourth with the first 
abdominal correct. This view is still further supported by the 
suggestion of Grassi that the symphyloid ancestor of the Insecta 
had paired genital apertures at the hinder end of the body and 
also another pair between the third and fourth pairs of legs. 
That the genital openings among the hexapods are not very 
fixed in position is evident from the variety of conditions found 
in the different members of the group. Wheeler ('93) shows 
that the openings of the male and female differ, and an actual 
movement takes place in the former from the tenth to the ninth 
abdominal segment during embryonic life. 
