17 
the sexual gland is said to be in an abnormal condition, sterile 
— at least at the actual time when they came under exami- 
nation; while the sexual glands in my two male pigeons appear 
quite normal, able to enter into function in due time. 
Possibly I may have overlooked some cases recorded elsewhere, 
but already the number of instances related here tends to show 
that pseudohermaphroditism in birds is less rare in the female than 
in the male sex. This fact I think may now to a certain degree 
be explained, if we remember that the Wolffian ducts normally, 
at least for a long while, are preserved in female birds: a slight 
alteration in the conditions governing the fate of these ducts (and 
of the mesonephric remnants connected with them) may stop their 
retrogressive involution, and if this stoppage does not set in too late, 
a slight progressive evolution may take place to the effect that a 
more or less complete likeness to the seminal ducts (and the epi- 
didymis) in the male is acquired. In the male sex on the other 
hand the Miillerian ducts normally atrophy early in embryonic life 
and not the least trace seems to be present at the time of hatch- 
ing. Thus the possibility of becoming a pseudohermaphrodite in 
later life, which may be open to females, is excluded for males.) 
Hitherto I have only dealt with cases of pseudohermaphroditism. 
For sake of completeness I may add that also cases of true her- 
maphroditismus are known to occur among birds, but apparently 
Very rarely. As the records of such cases are widely spread and 
never seem to have been collected, I shall give the following brief 
notes. The cases recorded may be grouped in (1) those where both 
male and female sexual glands have been found in the same indi- 
vidual; and (2) those where the same sexual gland contained male 
and female elements. 
(1) Almost all of the first group are cases of Hermaphroditis- 
Mus verus lateralis, i. e. the specimens are in possession of a 
1) I shall not here enter into any discussion of the hypothesis set forth by 
rjan Olsen, that the internal secretion, supposed to be delivered by 
the "pars sexualis" of the Wolffian duct (fle deltaf Chappellier, 1. e. 
the parovarium resp. epididymis) is the main factor in producing secon- 
dary sexual characters and thus the phenomena of arrhenoidia, resp. the- 
lyidia. I think, however, that this hypothesis, in spite of the many indicia 
collected by Ø. Ol lsen, is far from being prov 
Vidensk. Meddel. fra Dansk naturh. Foren. Bd. 68. 2 
