But I must make a reservation here; it is not universally true of parthenogenetic eggs that maturation takes place without the second polar division. The first exception was observed in the salt-water crustacean, _Artemia salina_. In this case only one polar body is actually extruded and the number of chromosomes remains normal, as I was able to demonstrate with the small number of ova at my disposal; but according to the investigations of Brauer on more abundant material it appears that, while the second polar division is suppressed in the majority of the ova, and the external extrusion of a second polar body never occurs, the second polar division does nevertheless sometimes take place. The two daughter-nuclei arising from this division unite again immediately afterwards to form a single nucleus, and this now functions as a segmentation nucleus. Of course it again contains the full number of chromosomes, namely, twice 84=168. In _Artemia_, therefore, the adaptation of the ova to parthenogenetic development is not yet fully established, and the complete abandonment of the second polar division seems to be phyletically striven for, since, although the division still takes place, its effect is neutralized immediately afterwards. [Illustration: FIG. 78. Diagram of the maturation of a parthenogenetic ovum. The number of chromosomes normal to the species has been assumed to be four. _Uei_, a primitive germ-cell. _M Eiz_, a mother-egg-cell, with twice the normal number of chromosomes. _Eiz_, mature ovum after the separation of the first and only polar body. _Rk_^1.]