to 
ARTHUR BOLLES LEE 
The chromonema theory conceives of the chromo- 
some as composed (at least at a certain stage) of a continuous 
filiform chromatic element—often spirally coiled—supported 
on an achromatic core, or contamed in an achromatic cylindrical 
matrix. 
This notion is due to Baranetzky, who in 1880 (‘ Bot. 
Zeitung’, p. 241) described and figured, in the pollen mother- 
cells of Tradescantia virginica, a fine chromatic fibre 
spirally coiled, at the surface of the chromosomes, round an 
achromatic core. 
In 1901 Janssens (‘ La Cellule’, t. xix, pp. 55 and 58) de- 
scribed similar chromatic spirals uncoiling themselves from the 
chromatin clumps of the resting spermatogonia of the newt, 
and even figured similar filaments coiled within the chromosomes 
of the telophase, closely appled to an envelopmg membrane. 
Later (* La Cellule’, t. xxu, 1905, p. 418 and figs. 42 to 50 and 
52 to 55) he figured achromatic membranes clearly existing 
around the ‘ pachytene’ chromosomes of the auxocytes of 
Batrachoseps attenuatus, and concluded that in the 
stages of the bouquet and the strepsmema all the chromo- 
somes are in contact with their neighbours by means of these 
membranes— les chromosomes se touchent tous ’. 
Bonnevie (‘Arch. Zellforsch.’, 1, 1908, p. 450, and particu- 
larly pp. 471, 478, 477, 479, 509 ; 11, 1908, p. 201, and particu- 
larly pp. 266-70 ; 1x, 1913, p. 483) from a study of chromo- 
somes of Ascaris, Allium, and Amphiuma, deduces 
the following conclusions : A prophasic chromosome consists of 
an achromatic core on the surface of which is spread a con- 
tinuous mantle of chromatin (I find no mention of a membrane). 
In the telophase this mantle becomes differentiated into a 
spirally coiled thread, whilst the achromatin is cast out ito the 
new nucleus. The spiral threads of chromatin then put forth 
lateral processes which anastomose with those of neighbouring 
threads, and so form a nuclear network. At the next prophase 
the anastomoses are withdrawn, the chromatin threads shorten 
and thicken, and differentiate mto chromosomes showing a 
newly formedachromatic core with a continuous mantle of 
