554 Lewis. — The Behaviour of the Chromosomes 
Moenkhaus, W. J. (’04) : The Development of the Hybrids between Fundulus heteroclitus and 
Menidia notata with especial reference to the Behaviour of the Maternal and Paternal 
Chromatin. Am. Journ. Anat., iii, p. 29, 1904. 
Mottier, D. M. (’97) : Beitrage zur Kennlniss der Kerntheilung in den Pollenmutterzellen einiger 
Dikotylen and Monokotylen. Jahrb. wiss. Bot., xxx, pp. 169-204, 1897. 
= — — t — “ (’03) : The Behaviour of the Chromosomes in the Spore Mother-Cells of Pligher 
Plants and Embryosac Mother-Cells. Bot. Gaz., xxxv, pp. 250-82, 1903. 
• (’07) : The Development of the Heterotype Chromosomes in Pollen Mother-Cells. 
Ann. Bot., xxi, pp. 309, 347, 1907. 
Overton, J. B. (’05) : Uber Reductionsteilung in den Pollenmutterzellen einiger Dikotylen. Jahrb. 
wiss. Bot., xlii, pp. 121-53, I9°5- 
Rosenberg, O. (’04) : Uber die Individualist der Chromosomen im Pflanzenreich. Flora, xciii, 
pp. 251-9, 1904. 
(’04) : Das Verhalten der Chromosomen in einer hybriden Pfianze. Ber. Deutsch. 
Bot. Ges., xxi, p. no, 1904. 
— — — (’04) : Uber die Tetradenteilung eines Drosera-Bastardes. Ber. Deutsch. Bot. Ges., 
xxii, p. 47, 1904. 
Schaffner, J. H. (’97) : The Division of the Microspore Nucleus (of Lilium philadelpliicuni). 
Bot. Gaz., xxiii, pp. 430-52, 1897. 
(’06) : Chromosome Reduction in the Microsporocytes of Lilium tigrinum. Bot. 
Gaz., xli, pp. 184-90, 1906. 
(’07) : Synapsis and Synizesis. The Ohio Naturalist, vii, pp. 41-8, 1907. 
Strasburger, E. and Mottier, D. M. (’97) : Uber den zweiten Theilungsschritt in Pollenmutter- 
zellen. Ber. Deutsch. Bot. Gesellsch., xv, p. 327, 1897. 
Strasburger, E. (’95) : Karyokinetische Probleme. Jahrb. wiss. Bot., xxviii, p. 151, 1895. 
(’04) : Uber Reductionsteilung. Sitzber. Kon.-Preuss. Akad. Wiss., xviii, pp. 
587-614, 1904. 
■ (’05): Typische und allotypische Kerntheilung. Jahrb. wiss. Bot., xlii, pp. 1-71, 
I 9°5- 
Sutton, W. S. (’03): The Chromosomes in Heredity. Biol. Bull., iv, p. 231, 1903. 
Wilson, E. B. (’05«) : Studies on Chromosomes. I. The Behaviour of the •Idiochromosomes in 
Hemiptera. Journ. Exp. Zool., ii, p. 371, 1905. 
(’05£) : II. The Paired Michromosomes, Idiochromosomes and Heterotype Chro- 
mosomes in Hemiptera. Journ. Exp. Zool., ii, p. 507, 1905. 
EXPLANATION OF FIGURES IN PLATES XXIX AND XXX 
Illustrating Mr. Lewis’s Paper on the Chromosomes in Pinus and Thuja. 
All figures were drawn from sections with the aid of a camera lucida and with a Lietz apochro- 
matic 2 mm. objective, 1*30 apert. Figs. 8, 13, 14, 16, 18 with compens. oc. 18; all others with 
compens. oc. 12. 
Fig. r. Pollen mother-cell of Pinus Strobus prior to synapsis. The chromatin is disposed 
throughout the cavity in the form of rather large lumps. No indication of pairing of the chromo- 
meres or the linin threads. The number of chromomeres exceeds the number of somatic chromosomes 
of the species. 
Fig. 2. A cell from the same anther loculus. The nuclear network is beginning the contraction 
which indicates that the synaptic phase is approaching. No indications of a spirem are evident. The 
chromomeres show no disposition to unite in pairs. Two nucleoli are present. 
Fig. 3. The nuclear content is becoming more densely contracted. The chromomeres are 
beginning to appear as if their material was being spun out along the linin strands connecting them. 
The content is still a reticulum. 
