1. The multivalent configurations in the triploid and tetraploidLycopersicum esculentum are of the types which would be expected, if they were determined by a random distribution of chiasmata.

2. They vary in frequency from cell to cell, but remain statistically constant at successive stages, as they would be expected to do on this assumption.

3. The configurations (contrary to the opinion of previous authors, but as is expected on analogy with all other cases of chiasma pairing) are constant between diplotene and metaphase.

4. The metaphase chiasma frequency is highest in the diploid and lowest in the triploid. This is attributed to a similar difference in original chiasma frequency rather than to a greater reduction in number in the triploid during terminalisation.

5. The curve of variance is higher in the polyploids than in the diploids, as has previously been found inTulipa andHyacinthus.

6. The formation of trivalents and univalents in the triploid gives rise to irregularities in the second division, and to the formation of restitution nuclei.

7. The formation of quadrivalents in the tetraploid leads to numerical non-disjunction which is reflected in reduced fertility.

The somatic chromosomes ofAesculus Hippocastanum (2n = 40) and ofAe. Pavia (2n = 40) are exactly similar in size and shape, although each complement contains within it differences which are also distinguishable in the complement of the hybridAe. carnea (2n = 80).

1. The basic haploid chromosome number in the genusTulipa is 12. Polyploid series occur in both the subsections Eriostemones and Leiostemones.

2. Although the diploid species probably reproduce sexually in the wild, the polyploids must be purely clonal since no aneuploids have been found.

3. Two main types of change have affected the chromosome morphology of the genus. Genotypic change of size and regulated structural change altering the position of the centromere have separated the genus into three groups with large, medium and small chromosomes. Random structural change has produced complements with reduplicated fragments (T. galatica) and with clearly unmated chromosomes (T. Gesneriana var. Zomerschoon).

4. Evidence from external and chromosome morphology, from intersterility and from the time at which meiosis occurs, points to the conclusion that the subgroupClusiana of the Leiostemones is as distinct from the other subgroups as it is from the Eriostemones.

1. The tetraploid tulip species have a lower chiasma frequency at meiosis than the diploids and triploids and fewer changes of partner at pachytene than the latter. Consequently although autotetraploid, they form few quadrivalents and are sexually fertile.

2. The quadrivalents that they form may be classified in two ways:

3. The inter- and intranuclear mean squares show no significant correlation of chiasma frequency in the diploids. A slightly positive correlation in the tetraploids and variable correlation in the triploids is presumably to be attributed to the number of changes of partner their chromosomes undergo and to variable external conditions.