The Somatic Mitoses in Hyacinthus orientalus var. albulus. 375 
but such a phenomenon occuring, as it does, witk such frequence makes 
it probable that it is not the entire chromosome which carries the here- 
ditary characters but some smaller unit of which the chromosome is an 
aggregation. This may well be something intermediate between the 
chromosome and the chromomere, for in Hyacinthus no definitely marked 
chromomeres are visible such as have been seen in many other forms, 
the spireme and the reticulum both exhibiting a marked homogeneity 
in substance throughaut the prophase, with the one exception of the 
thinner centre leading to the longitudinal fission. 
Such a phenomenon suggests the possibility that the permanence 
of the entire chromosome is not essential to the preservation of the here- 
ditary type, but that the “segments” may retain their individuality, 
even if they are not always combined in the same groups, or chromosomes. 
In conclusion I should like to express my thanks for valuable advice 
and criticism to Dr. H. C. I. Gwynne-Vaughan (Fraser) at whose Sug- 
gestion the work was undertaken. 
Summary. 
1. The reticulum in the resting stage is fine, and fairly homogeneous 
in character with no indication of pro-chromosomes. 
2. In the prophase the cross-connections of the reticulum break, 
and a ragged spireme is formed with diamond-shaped spaces along the 
centre line. From this is developed a smooth ribbon, in which the fission 
is temporarily obliterated, but the fission re-appears before the Segmen- 
tation of the thread into 16 chromosomes. 
3. The constriction of the chromosomes into separate segments is 
of common occurrence throughout mitosis. 
4. On reaching the poles the daughter chromosomes join end to 
end, and put out lateral processes, at the same time Splitting down the 
centre, so that a definite spireme is formed before the reticulum is re- 
constituted. 
5. The occurence of paired chromosomes is so rare that there is no 
justification for regarding it as other than accidental. 
List of Papers. 
1. 1910. Digby, L. The Somatic, Premeiotic and Meiotic Divisions of Galtonia 
candicans. Ann. Bot. Vol. XXIV. p. 727. 
2. 1911. Fraser, H. C. I. and Snell, J. The vegetative divisions in Vicia Faba. 
Ann. Bot. Vol. XXV. p. 845. 
3. 1912. Gates, R. D. The Somatic Mitoses in Oenothera. Ann. Bot. Vol. XXVI. 
