equally divided between males and females. Fertile eggs were 
found 50 days following a single insemination, which indicated 
a normal duration of fertility. Olsen recently reported (1961) 
that the frequency of parthenogenesis in turkey eggs could be 
significantly increased by Rous sarcoma virus. 
Another alteration of the normal genetic endowment 
is the phenomenon of sex reversal. Newcomer et al. (1960) con- 
ducted an investigation of a genetic female which had laid eggs 
while on the farm, but later developed the secondary sexual 
characteristics of a male. They found one gonad on the left 
filled with tubules active in spermatogenesis. The morphology 
and size of the spermatozoa, however, were so unnatural as to 
indicate little, if any, functional possibilities. They sug- 
gested that this unnatural morphology and size indicated 
polyploidy. 
A final alteration in spermatogenesis as related to 
genetics is that found in hybrids. Many observers are in agree- 
ment that spermatogensis in hybrid birds may be fairly normal up 
to the first reduction division. The second reduction division 
frequently does not occur in hybrid birds such as domestic dove 
and magpie pigeon cross; instead, the secondary spermatocytes 
become converted into giant spermatids which in turn are trans- 
formed into spermatozoa of approximately twice normal size. 
Sterile hybrids of the muscovy duck and mallard duck occasion-= 
ally undergo normal meiosis which proceeds through the first 
maturation division. However, the resulting secondary sper-~ 
matozoa degenerate (Crew and Koller, 1936; cited by Romanoff, 
1960). Asmundson and Lorenz (1957) reported that over 30 each 
of turkey-pheasant hybrids and chicken-pheasant hybrids raised 
were all sterile. In reports of avian hybrids, males predominate. 
5. Hormones. 
The activity of the bird's gonads is controlled by 
the secretion of the pituitary gland. fThis gland, stimulated 
by neural reception of light results in secretion of gonadotropin, 
which in turn acts upon the testes. The importance of the 
pituitary can be illustrated by its removal, which causes testice 
ular atrophy in birds (Hill et al., 1934). The administration 
of either whole pituitary extracts or of purified F.5.H. causes 
enlargement of the testes. Wild birds out of breeding season are 
unresponsive to administration of gonadotropic hormone. 
Androgens depress the pituitary and the resulting lack 
of gonadotropic hormone causes the involution of spermatocytes, 
but not of spermatogonia (Kumaran and Turner, 1949). Moreng et 
al. (1956b) found that injection of estrogen into the male, re- 
duced testis weight and inhibited production of spermatocytes, 
presumably by depressing secretion of pituitary gonadotropin 
(Kumaran and Turner, 1949, Moreng et al., 1956b). van Teinhoven 
(1957) found that testis weights were significantly decreased 
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