176 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 
in Fig. 43 there occurs an outflow of clear matter from the 
cytoplasm, just as in membrane formation. This is quickly 
followed by the clearing and swelling of the whole egg, until at 
last it becomes a “shadow” (Figs. 44 and 45). The variations 
that present themselves on examination of a quantity of eggs 
in the saponin solution occur principally in the membrane 
formation. In many cases the formation of vesicles, which is 
here depicted in Figs. 40 and 41, did not take place. Instead 
of this, the egg proceeds from the stage drawn in Fig. 39 directly 
into the stage of membrane formation (Fig. 42). As an inter- 
mediate stage one observes cases in which only a roughening 
of the surface of the egg takes place, owing to the formation 
of numerous minute drops, which suddenly swell simultaneously 
and give rise to the formation of the surface membrane; at first 
this is closely adjacent to the cytoplasm, but as a Sec of the 
osmotic pressure more sea-water is always flowing in, until the 
e 
tension of the membrane counterbalances the osmotic pressure. 
The examination of these drawings also gives the impres- 
sion that the effect of the saponin is produced in two distinct 
stages, which do not necessarily merge continuously into each 
other; Ghe first stage is probably the effect upon the surface of 
the egg, leading to membrane formation, and the second is 
obviously an effect produced upon the interior of the egg, and 
leads to cytolysis. In both cases the liquefaction is associated 
with a swelling and increase in volume. 
When eggs that have been treated with saponin until 
membrane formation has taken place are freed from the last 
trace of saponin by washing them four to six times in pure 
sea-water, they behave just like eggs in which the artificial 
membrane has been produced by a fatty acid. If they are left 
in sea-water, development starts, and the stage to which they 
develop depends on the temperature. If they are subsequently 
treated for about forty minutes (at 15°C.) with hypertonic 
sea-water, they develop into larvae. 
