, the eggs will segment and develop
normally, when transferred back to normal sea-water. If care is taken,
practically all the eggs can be caused to develop into plutei, the
majority of which may be perfectly normal and may live as long as larvae
produced from eggs fertilised with sperm.

It is obvious that the sea-urchin egg is injured in the process of
membrane-formation and that the subsequent treatment with a hypertonic
solution only acts as a remedy. The nature of this injury became clear
when it was discovered that all the agencies which cause haemolysis,
i.e. the destruction of the red blood corpuscles, also cause
membrane-formation in unfertilised eggs, e.g. fatty acids or ether,
alcohols or chloroform, etc., or saponin, solanin, digitalin, bile
salts and alkali. It thus happens that the phenomena of artificial
parthenogenesis are linked together with the phenomena of haemolysis
which at present play so important a role in the study of immunity. The
difference between cytolysis (or haemolysis) and fertilisation seems to
be this, that the latter is caused by a superficial or slight cytolysis
of the egg, while if the cytolytic agencies have time to act on the
whole egg the latter is completely destroyed. If we put unfertilised
eggs of a sea-urchin into sea-water which contains a trace of saponin we
notice that, after a few minutes, all the eggs form the typical
membrane of fertilisation. If the eggs are then taken out of the saponin
solution, freed from all traces of saponin by repeated washing in normal
sea-water, and transferred to the hypertonic sea-water for from 35 to
55 minutes, they develop into larvae. If, however, they are left in
the sea-water containing the saponin they undergo, a few minutes after
membrane-formation, the disintegration known in pathology as CYTOLYSIS.
Membrane-formation is, therefore, caused by a superficial or incomplete
cytolysis. The writer believes that the subsequent treatment of the egg
with hypertonic sea-water is needed only to overcome the destructive
effects of this partial cytolysis. The full reasons for this belief
cannot be given in a short essay.

Many pathologists assume that haemolysis or cytolysis is due to a
liquefaction of certain fatty or fat-like compounds, the so-called
lipoids, in the cell. If this view is correct, it would be necessary to
ascribe the fertilisation of the egg to the same process.

The analogy between haemolysis and fertilisation throws, possibl