| $34 ^ The American Naturalist. [Ocicber, 
‘ease with two Heterodon platyrhinus, (spotted adders), which were 
i brought to me with the organs projected so as to present the 
spines. They were caught by a cat, and were represented -to 
"me as fighting their captor in this and other ways. Snakes 
are, however, very careful not to present these organs fully 
 evaginated so as to expose the delicate structures near the apex. 
I have never seen this to be the case in an alcoholic specimen, 
(with one possible exception), and I should judgethat this was 
the general experience, from the figures given by authors. It 
is said that male snakes may be compelled to project the hemi- 
penes by holding them before a fire, but I have not seen this. 
The hemipenis of the Ophidia is traversed by a groove which 
divides the superficial investment to the internal integument 
(or external integument when the organ is retracted), which 
‘commences at the base internally, and soon turns to the exter- 
. nal side of the organ and continues to its extremity. This is 
the sulcus spermaticus (ssin Plate xxvii) This sulcus is 
always bifureated in venomous snakes, and I find it to be 
equally bifurcated in many harmless snakes (Figs. 2, 3, 7). 
The investing tissues may or may not correspond with this 
bifurcation. Thus the hemipenis may be more or less bifur- 
cate (Figs. 1, 2, 7, 9, 10, 11). Schlegel states that it is bifurcate 
in venomous snakes, but it is not so in the sea-snake Hydro- 
phis hardwickii, nor in Bungarus semifasciatus, Hoplocephalus 
coronatus, ete., while it is bifurcate in many non-venomous forms. 
Next to the bifurcation of the sulcus in importance, is the 
nature of the surface of the external investment (internal when 
retracted). In the most perfect types both venomous and non- 
venomous, this surface is reticulate like tripe, the enclosed 
areas forming calyces, which may have a suctorial function 
(Figs. 6, 9, 10, 11). Their borders are often papillose, and are 
sometimes so deeply divided into papille as to lose their 
original character. These papille may be the seat of osseous 
deposit, becoming bristles or spines, (sp), which become larger 
toward the middle of the length, and lose their mutual mem- 
branous connections. These isolated spines may extend to the 
apex, but they rarely extend to the base. The surface may, 
however, be laminate and not reticulate, and the laminz may 
