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GLOSSARY 



Leucoplas'tids (Xet-Kos, white; TrAaoros, form), the colourless plastids of plant- 

 cells from which arise the starch-formers (amyloplastids), chloroplastids, and 

 chromoplastids. (Schimper, 1883.) 



Li'nin (linum, a linen thread), the substance of the "achromatic" nuclear 

 reticulum. (Schw'ARZ. 1887.) 



Maturation, the final stages in the development of the germ-cells. More spe- 

 cifically, the processes by which the reduction of the number of chromosomes 



is effected. 



Metakine'sis (see Metaphase) duera, beyond {i.e. further) ; K^vvrjcn^, movement), 

 the middle stage of mitosis, when the chromosomes are grouped in the equa- 

 torial plate. (Flemming, 1882.) 



Metanu'cleus, a term applied to the egg-nucleus after its extnision from the 

 germinal vesicle. (Hacker, 1892.) 



Met'aphase, the middle stage of mitosis during which occurs the splitting of the 

 chromosomes in the equatorial plate. (Strasburger, 1884.) 



Met'aplasm (/xera. after, beyond; TrAacr/Lia, a thing formed), a term collectively 

 applied to the lifeless inclusions (deutoplasm, starch, etc.) in protoplasm as op- 

 posed to the living substance. (Hanstein, 1880.) 



Micel'la, one of the ultimate supra-molecular units of the cell. (Nageli, 1884.) 



Microcen'trum. the dynamic centre of the cell, consisting of one or more centro- 

 somes. (Heidenhain. 1894.) 



Mi'cropyle (^i/cpds, small; ttvXt], orifice), the aperture in the egg-membrane 

 through which the spermatozoon enters. [First applied by TuRPiN, in 1806, 

 to the opening through which the pollen-tube enters the ovule, t. Robert 

 Brown.] 



Mi'crosome (/xtKpo?. small ; aw/xa, body), the granules as opposed to the ground- 

 substance of protoplasm. (Hanstein, 1880.) 



Middle-piece, that portion of the spermatozoon lying behind the nucleus at the 

 Iwse of the flagellum. (Schweigger-Seidel, 1865.) 



Mid-body (•• Zwischenkbrper"). a body or group of granules, probably comparable 

 with the cell-plate in plants, formed in the equatorial region of the spindle during 

 the anaphases of mitosis. (Flemming, 1890.) 



Mi'tome (/Atrcofta, from /aitos, a thread), the reticulum or thread-work as opposed 

 to the ground-substance of protoplasm. (Flemming, 1882.) 



[Mitoschi'sis] du-tro?, thread; cr;>^t'^etv, to split), indirect nuclear division; mito- 

 sis. (Fle.mming, 1882.) 



Mito'sis (|U,tTo?. a thread), indirect nuclear division typically involving: a. the 

 formation of an am]3hiaster; ^, conversion of the chromatin into a thread 

 (spireme) ; c, segmentation of the thread into chromosomes ; d, splitting of the 

 chromosomes. (Flemming, 1882.) 



Mi'tosome (ixlto?, a thread ; (rw/xa, body), a body derived from the spindle-fibres 

 of the secondary spermatocytes, giving rise, according to Platner, to the mid- 

 dle-piece and the tail-envelope of the spermatozoon. Equivalent to the Neben- 

 kern of La Valette St. George. (Platner, 1889.) 



Nebenkern (Paranucleus), a name originally applied by Blitschli (1871) to an 

 extranuclear body in the spermatid; afterwards shown by La Valette St. George 

 and Platner to arise from the spindle-fibres of the secondary spermatocyte. 

 Since applied to many forms of cytoplasmic bodies (yolk-nucleus, etc.) of the 

 most diverse nature. 



Nuclear plate, i. The equatorial plate. (Strasburger. 1875.) 2. The parti- 

 tion-wall which sometimes divides the nucleus in amitosis. 



Nucleic acid, a complex organic acid, rich in phosphorus, and an essential 

 constituent of chromatin. 



