GLOSSARY 63 



HAPLOiD. Haploos, single. Applied to the reduced or gametic 

 number of chromosomes. 



HAPLO-DiPLOiD SYSTEM. That in which the sexes are distinguished 

 in that one is haploid, the other diploid. 



HERMAPHRODITE. Hermaphroditos, combining both sexes. An 

 organism with both male and female reproductive organs. 



HETEROGAMETic. Heteros, other; gametes, spouse. Elaborating 

 gametes of two kinds in respect of the elements of the sex- 

 determining mechanism. 



HETEROKiNESis. Heteros, other; kinesis, change or movement. 

 That meiotic division in the course of which the sex-produc- 

 ing gametes become separated by differential distribution of 

 the sex-chromosomes. 



HETEROPYCXOSis. Heteros, other; pyknos, dense. Precocious con- 

 densation of certain chromosomes in the prophase especially 

 of meiosis. 



HETEROTYPIC DIVISION. The first meiotic division (falling into disuse). 



HETEROZYGOTE. Heteros, other ; sygon, yolk. A Mendelian hybrid 

 in whose genetic constitution there are one or more recessive 

 genes and which, therefore, does not breed true. The off- 

 spring of a mating of parents which differed one from the 

 other in respect of one or more allelomorphic characters. 



HOMEOTYPic DIVISION. The sccond division of meiosis (falling into 

 disuse). 



HOMOGAMETIC. Homos, alike; gametes, spouse. Elaborating garnetes 

 all of a kind in respect of the elements of the sex-determining 

 mechanism. 



HOMOZYGOTE. Homos, alike; zygon, a yolk. An individual in whose 

 genetic constitution each gene is present in the duplex state. 

 The offspring of a mating of two parents genetically identical 

 in respect of one or more Mendelian characters. 



KARYOGAMY. Karyoti, nucleus; gametes, spouse. Fusion or nuclei at 

 the fertilization of an egg by a sperm. 



KARYOKiNESis. Karyoti, nucleus; kinesis, change or movement 

 (=mitosis). 



MATRICLINOUS. Mater, a mother. Inclining heredity toward the 

 maternal side. 



MATURATION. The ripening or final stages in the formation of the 

 gametes by meiosis. 



MEIOSIS. Meiosis, reduction. A form of mitosis in which the nucleus 

 divides twice and the chromosomes once. 



MIDDLE PIECE. A term of vague meaning applied to the middle 

 region of the sperm. 



MITOSIS. Mitos, a thread. The process by which the daughter 

 chromosomes are separated into two groups. 



NON-DISJUNCTION. The failure of separation of paired chromo- 

 somes at meiosis and their passage to the same pole. 



OOCYTE. Oon, an egg. The egg cell prior to the completion of the 

 maturation process. 



