nistic relationship between the nuclear element coming from the male parent 
and the cytoplasm of the female parent. In cases where the chromosomal dis- 
simil-rity between the parent species is very large and the nuclear elements 
are not harmonious, the degeneration of the hybrid germ cells occurs very early 
in meiosis, as in Gallus X Phasianus. If the chromosomal dissimilarity between 
the parents is small and the nuclear cytoplasmic relation is quite harmonious, 
the degeneration of the hybrid germ cells takes place in the latter stage of 
meiosis, as in Syrmaticus X Chrysolophus. 
1943 "Studies on Sterility in Hybrid Birds, VI, Cytological Studies on the Anterior 
Lobe of the Hy», ophysis in some Hybrid Birds" (with English summary): Jour Fac Sci 
Hok Imp Univ, IX (1), pp 77-84, 2 pl, Jun 1943. 
The cytology of the anterior lobe of the hypophysis in three forms of generic 
hybrids, Callus X Fhasianus, Anas X Cairina, and Chrysolophus X Phasianus, was 
studied to determine the morphological correlation between the hypophysical 
changes and development of the gonads. (1) The anterior hypophysis of the male 
of the Gallus X Phasianus cross is. intermediate in cytological structure between 
the mixture and the castration types. The male of Anas X Cairina belongs to the 
intersex type, while the female possesses a hypophysis intermediate between the 
normal and intersex types. In Chrysolophus X Pnasianus the anterior hypophysis 
may be either of the castration type or intermediate between the intersex and 
castration types. (2) Cytologically the secretion of the gonad-etimulating 
harmones in the anterior hypophysis of these hybrids seem functionally similar to 
that of pure line birds. Thus the inactive growth of germ cells or their aberrant 
behavior in hybrids is not caused by the inactivity of the hormone secretion from 
the anterior hypophysis but by characteristics in the germ cells themselves. (3) 
The male of the hybrid, Anas X Cairina, possesses well-developed testes and healthy 
seminal tubules, with spermatogonia in active division and normal anxocytes. The 
hypophysis belongs in structure to the intersex type. This suggests that the har- 
mones which act to control the castration change of the anterior hypophysis may be 
secreted from the germ tissue at a considerably later stage of spermatogenesis. 
1943 "A Proposed New Systematics in Birds Based on Studies of Hybrid Sterility": ptl 
Kagaku, XIII (6), pp 202-207, 234-239, 17 fig, June 1943; pt 2 Kagaku, XIII (7), 
pp 234-239, Jul 1943. 
The classification of birds* based on morphological characters alone is not 
justifiable. Certain species closely resembling one another are often quite 
distantly related. Others, such as domestic fowl, although diverse in appearance 
are in reality quite close. Systematists classify their birds into families, 
genera, species, and subspecies: without conclusive definitions of the amount or 
nature of the differences characteristic of each rank. The author's studies of 
the germ plasm of hybrids to determine the cytological cause of consequent steri- 
lity assist in establishing definitive criteria between the various ranks. The 
fertility of hybrid offspring varies with the relative closeness of the system- 
atic position of its parents. Strangely, the F, male hybrids show this point 
more clearly than’either the females or the Fos. The three reasons for hybrid 
sterility are: (1) failure of meiotic division owing to asymmetry of the cor- 
responding chromosomes or other abnormalities; (2) disharmony between female 
cytoplasm and the male chromosome; (3) an “intersex” condition owing to lack of 
balance between the sex-detormining factor of both parents.~ Hybrid sterility 
caused by (1) and (2) is similar, shown by both sexes, and indicative of systen- 
atic affinities, while that resulting from (3) is limited to females in the Fy 
generation, appears in both sexes in the Fo, and has no ccnnection with systen- 
atic affinity. 
In determining the systematic relationship of the parents, only Fy male hybrids 
are of value. If the Fy male hybrid is completely fertile, the writer considers 
both parents conspecific. If the Fj male shows a slight degree of fertility, 
the parents are considered specifically distinct but generically alike. If the 
