758 The Amerwan Naturalist. [August, 
connected with sexual excitement. One instance of a way in which 
the reproductive maturity is known to effect a by no means obviously 
related result may be given. Every field-naturalist knows that the 
male stickleback builds a nest among the weeds, and that he weaves 
the material together by mucous threads secreted by the kidneys. The 
little animal is also known to have strong passions ; it is polygamous 
in relation to its mates, and most pugnacious in relation to its rivals. 
Professor Möbius has shown that the male reproductive organs (or 
testes) become very large at the breeding season, and that they press in 
an abnormal way upon the kidneys. This encroachment produces a 
pathological condition in the kidneys, and the result is the formation 
of a mucous secretion, somewhat similar to what occurs in renal dis- 
ease in higher forms. To free itself from the irritant pressure of this 
secretion the male rubs itself against external objects, most cgn- 
veniently upon its nest. Thus the curious weaving: instinct does not 
demand nor find rationale in the cumulative action of natural selection 
upon an inexplicable variation, but is traced back to a pathological 
and mechanical origin in the emphatic maleness of the organism. The 
line of variation being thus given, it is of course conceivable that 
natural selection may have accelerated it. 
‘So, too, though again the physiological details are scanty, the 
superabundant growth of hair and feathers may be interpreted, in 
some measure, through getting rid of waste products, for we shall see 
later how local katabolism favors cell multiplication. Combs, wattles, 
and skin excresences point to a predominance of circulation in the 
skin of the feverish males, whose temperatures are known in some 
cases to be decidedly higher than those of females. Even skeletal 
weapons like antlers may be similarly interpreted; while the exag- 
gerated activity of the soglasni | is another —— for excreting 
waste, 
‘t [In regard to horns, feathers, and the like, in association with vigor- 
ous circulation, two sentences from Rolph may be quoted: ‘The 
exceedingly abundant circulation which periodically occurs in the at 
first soft frontal protuberances of stags admits and conditions the 
colossal development of horn and ensheathing velvet.. . . In the 
same way the rich flow of blood in the feather papillae conditions the 
immense growth of the feathers, . . . and the same is true of hairs, 
spines, and teeth. 
** Some of the even subtler differences bet th are of interest 
in illustrating the general antithesis. Ell in the love-lights of the 
Italian glow insect (Luciola) the color is said to be identical in the 
