GLOSSARY 341 



Pseudoiiu'clein (see Nuclein), the same as the paranuclein of Kossel. (HAM- 



MARSTEN, 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 the number 



of chroraosomes in maturation. (RUCKERT, 1894.) 

 Pyre'niii (Trvprjv. 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 (Trvpirjv, 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. (SCHMITZ, 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 the mammalian 



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



matoblast" as originally used by VON EBNER, 1871.) 

 Sper'matid (o-Tre'p/xa, seed), the final cells which are converted without further 



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



or " Samenmutterzellen." (LA VALETTE ST. GEORGE, 1886.) 

 Sper'matoblasts (cr7rep/xa, seed; /3AaoTos, 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. (VON EBNER. 1871.) 

 Sper'matocyst (o-Tre'p/xa, seed ; KVOTIS, 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.) 

 Sper'matocyte (oW/o/xa, seed; KVTOS, 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] (<r7rep/xa, seed; gemma, bud), nearly equivalent to spermato- 



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



LA VALETTE ST. GEORGE, 1878.] 

 Spermatogen'esis (o-Trep/xa, seed ; yeVe<ns, origin), the phenomena involved in 



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



process of reduction in the male. 

 Spermatogo'iiium (" Ursamenzelle " ) ((nrcp/ia, 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 (o-7rep/xa, seed; /xepos, a part), the chromatin-granules into 



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



Petromyzon, BOHM, 1887.) 

 Sper'matosome (o-Wp/xa, seed ; <ruj/xa, body), the same as spermatozoon. (LA 



VALETTE ST. GEORGE, 1878.) 

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



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

 Spermatozo'on (cr7rep/xa, seed ; a5ov, animal), the paternal germ-cell of animals. 



(LEEUWENHOEK, 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. HERTWIG, 1875.) 

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



