GLOSSARY 341 



Pseudonu'cleiii (see Nuclein). the same as the paranuclein of Kossel. (Ham- 



MARSTKX. 1894.) 

 Pseudo-reduction, the preliminary halving of the number of chromatin-rods as a 

 prelude to the formation of the tetrads and to the actual reduction in tlie number 

 of chromosomes in maturation. (RuCKERT, 1894.) 

 Pyre'nin {-n-vpi'^v. the stone of a fruit: i.e. relating to the nucleus), the substance 

 of true nucleoli. Equivalent to the paranuclein of Hertwig. (Schwarz, 1887.) 

 Pyre'noid {Trvprjv, the stone of a fruit; like a nucleus), colourless plastids (leuco- 

 plastids ). occurring in the chromatophores of lower plants, forming centres for 

 the formation of starch. (Sch.mitz, 1883.) 

 Reduction, the halving of the number of chromosomes in the germ-nuclei during 



maturation. 

 Sertoli-cells. the large, digitate, supporting, and nutritive cells of tlie mammalian 

 testis to which the developing spermatozoa are attached. (Equivalent to - sper- 

 matoblast"' as originally used by vox Ebxer, 1871.) 



Spermatid {cnrepixa, seed), the tinal cells which are converted without further 

 division into spermatozoa ; they arise by division of the secondary spermatocytes 

 or "Samenmiitterzellen." (La Valette St. George. 1886.) 



Sper'matoblasts {aTrep/xa, seed; /iJAaards. germ), a word of vague meaning, 

 originally applied to the supporting cell or Sertoli-cell. from which a group of 

 spermatozoa was supposed to arise. By various later writers used synonymously 

 with spermatid, (vox Ebxer, 1871.) 



Sper'matocyst (o-7re'p/i,a, seed ; Kuort?, bladder), originally applied to a group of 

 sperm-producing cells ("spermatocytes "), arising by division from an •• Ursa- 

 menzelle"' or "spermatogonium." (La Valette St. George. 1876.) 



Spermatocyte ( o-Trepjua, seed ; kv'tos, hollow^ (a cell)), the cells arising from the 

 spermatogonia. The primary spermatocyte arises by growth of one of the last 

 generation of spermatogonia. By its division are formed two secondary sper- 

 matocytes, each of which gives rise to two spermatids (ultimately spermatozoa). 

 (La Valette St. George. 1876.) 



[Spermatogem'ma] {cnr(.pp.a. seed; gemma, bud), nearly equixalent to spermato- 

 cyst. Differs in the absence of a surrounding membrane. [In mammals. 

 La Valette St. George, 1878.] 



Spermatogen'esis {(nvipp-a, seed; yeVecns. origin), the phenomena involved in 

 the formation of the spermatozoon. Often used more specifically to denote the 

 process of reduction in the male. 



Spermatogo'nium (" Ursamenzelle " ) {(Jiripjxa, seed; yovr/. generation), the 

 descendants of the primordial germ-cells in the male. Each ultimate sper- 

 matogonium typically gives rise to four spermatozoa. (La Valette St. 

 George. 1876.) 



Spermatome'rites (a-n-epixa, seed; /xepo?. a part), the chromatin-granules into 

 which the sperm-nucleus resolves itself after entrance of the spermatozoiin. (In 

 Petroiiiyson. Bohm. 1887.) 



Sper'matosome ( o-Trep/xu. seed; a^p-a, body), the same as spermatozoon. (La 

 \\vlette St. George, 1878.) 



Spermatozo'id (see Spermatozoon), the ciliated paternal germ-cell in plants. 

 Tlie word was first used by von Siebold as synonymous with spermatozoon. 



Spermatozoon {(j-Kkppxu seed; ^woi/, animal), the paternal germ-cell of animals. 

 (Lei:l\vk\hoek. 1677.) 



Sperm-nucleus, the nucleus of the spermatozoon ; more especially applied to it after 

 entrance into the egg before its union with the egg-nucleus. In this sense 

 equivalent to the -male pronucleus" of Van Beneden. (O. Hertwtg. 1875.) 



Sper'mocentre. the sperm-centrosome during fertilization. (FoL, 1891.) 



