Über die mitoseverhältnisse im Felchenei (Coregonus lavaretus L. Steinmann)

Summary

The new results described in the foregoing work were obtained by the smearing technique from the egg material of gwyniads (coregonids) coming from the Lake of Zurich and from the Lake of Constance (near Ermatingen). The results of these experiments deviate from those obtained up to now.

Thus an entire series of different chromosome numbers was discovered, as a rule, in one and the same embryo. In the majority of cases, these numbers do not have a definite relation to one another. This fact excludes an endomitotic polyploidization. However, if we consider only those numbers which come up frequently we can place them in series as multiples of 7 or 12. A dispersion around certain numbers is due to the phenomenon of non-disjunction.

The number 84 appears most frequently. A set of this number does not show groups of 4—contrary to the experiments ofSvaerdson andKupka. However, groups of 4 can be proven with some certainty on an analysed plate with 146 chromosomes. Consequently, there exists polyploidization through endomitoses in numbers exceeding at least 84.

Differences in the phases of the successive stages of mitosis as well as tripolar anaphases give indications to a certain mechanism of nucleus decrease, particularly, since in both phenomena the numbers of chromosomes involved can also be found as total chromosome number in smaller nuclei.

Today it is impossible to determine a definite chromosome number as being haploidic forCoregonus lavaretus L. (Steinmann) since no special experiments have been performed up to now.

However, since the number 84 appears most frequently, a certain preeminence can probably be given to it.

It appears that the mentioned deviations from the theoretical normal case are not abnormalities but should be considered as being normal in the development ofCoregonus lavaretus L. (Steinmann).