Diheterozygote — 43 — DIpygus 



Diplochlamydeous Chimaera. — A periclinal chimaera in 

 which the peripheral constituent is two layers of cells thick. 



Diplo-haploid Twinning. — A form of polyembryony in 

 which one embryo is diploid and the other haploid. 



Diploid. — (i) The somatic number of chromosomes (2n) as 

 opposed to the gametic (haploid) number (n). (ii) An or- 

 ganism whose somatic nuclei have two sets of chromosomes. 



Diploid Apogamety. — Euapogamy, diploid apogamy, q.v. 



Diploid Apogamy. — The formation of a diploid sporophyte 

 from a gametophyte without fertilization having occurred; 

 euapogamy. 



Diploid, Functional. — An allopolyploid which behaves as a 

 diploid in segregation (Darlington). 



Diploid Organism. — An individual possessing two haploid 

 sets of chromosomes in all of its somatic nuclei. 



Diploid Parthenogenesis. — See under Parthenogenesis. 



Diploid Set of Chromosomes. — A complement of chromo- 

 somes which consists of two equal haploid groups. 



Diploidisation. — A form of nuclear division, found in certain 

 fungi, by which the chromosome number is doubled. 



Diplokaryotic. — Possessing double the usual diploid number 

 of chromosomes; tetraploid. 



Diplonema. — The double chromosome thread at the diplo- 

 tene stage in meiosis. 



Diplont. — An organism during the diploid phase of its life- 

 cycle. 0pp. Haplont. 



Diplontic Sterility. — Sterility due to the production of 

 gametes which form inviable zygotes; zygotic sterility. 



Diplophase. — (i) Diplotene, q.v. (ii) The stage in the life- 

 cycle of an organism when the nuclei contain the diploid num- 

 ber of chromosomes. 



Diplosis. — A doubling of the gametic chromosome number. 



Diplosome. — (i) A paired heterosome. (ii) A double cen- 

 trosome outside the nuclear membrane. 



Diplospory. — The production of unreduced spores from 

 archesporial tissues. 



Diplotene. — The stage of meiosis following pachytene, at 

 which the four chromatids in each bivalent move apart in 

 two pairs but the two pairs remain adherent in the region of 

 chiasmata. 



Diprosopus. — A foetal monster which is characterized by the 

 presence of two faces. 



Dipygus. — A foetal abnormality characterized by a double 

 pelvis. 



