Haeckel's Law. — Biogenetic law, q.v. 



Haldane's Law. — When in the first generation between hy- 

 brids between two species, one sex is absent, rare, or sterile, 

 that sex is always the heterogametic sex. 



Half Race. — A "race" of plants whose phenotypic charac- 

 teristics are the result of the heterozygosity of certain genes. 

 Such a "race" can never breed true but always produces a 

 proportion of plants typical of the "race" in each generation. 



Half-spindle. — A uni-polar type of spindle occurring during 

 meiosis in some insects. 



Half Spindle Components. — Chromosomal fibres, q.v. 



Haplo-. — The term haplo-, followed by a symbol designating 

 a particular chromosome, indicates an individual in whose 

 somatic cells one member of this particular chromosome-pair 

 is lacking. Thus, in Drosophila, Haplo-IV means a fly in 

 which one member of the chromosome IV pair is missing. 

 cf. Diplo- and Triplo-. 



Haplobiont. — A plant in which there is no alternation of 

 generations so that there is only one type of individual in 

 the complete life-history. 



Haplochlamydeous Chimaera. — A chimaera in which the 

 epidermis forms one component and the inner tissues the other. 

 cj. Dichlamidius. 



Haplo-Diploid System. — A sex system in which one sex is 

 haploid and the other diploid. 



Haplodiplont. — A haploid spore-producing plant. 



Haploid. — Single; having the reduced number of chromo- 

 somes typical of gametes as opposed to the somatic number. 

 See Diploid Set of Chromosomes. 



Haploid Apogamety, Haploid Apogamy. — Reduced apo- 

 gamy, haploid parthenogenesis. See under Parthenogenesis. 



Haploid Incompatibility. — Homomorphic incompatibility 

 {q.v.) as between haploid individuals (as in the Fungi) in 

 which the diploid phase does not enter into the incompatibility 

 reaction. 



