xX 
ON A SIMPLE METHOD OF PRODUCING FROM ONE 
EGG TWO OR MORE EMBRYOS WHICH ARE GROWN 
TOGETHER! 
1. In the effort to extend my work on heteromorphosis 
to the embryo, I have discovered a simple method of pro- 
ducing at will from a single egg two or more embryos which 
are grown together. My experiments were made on sea- 
urchins, but it is possible that they can be made with just as 
great certainty on every other holoblastic egg. Ten minutes 
after having been artificially fertilized in normal sea-water, 
eggs of Arbacia were introduced into sea-water to which 
100 per cent. of its volume of distilled water had been 
added. The eggs absorbed so much water in the diluted sea- 
water that their membranes burst and part of their proto- 
plasm flowed out. The eggs then consisted of two connected 
spheres of protoplasm (P and P,, Fig. 69), as the extruded 
drop of protoplasm in consequence of its surface tension 
assumes a spherical form, as does the protoplasm remaining 
behind inside the membrane. As segmentation has not yet 
begun at this time, only one of the two droplets contained a 
nucleus (Fig. 69). When after some time I returned these 
eggs into normal sea-water, each of the two spheres of 
protoplasm developed into an entirely normal and complete 
embryo. 
In many cases the two embryos remained connected. 
More often, however, one of the embryos went to pieces in 
the course of its early development (in about the morula or 
blastula stage); and finally many double embryos were 
gradually separated from each other, in consequence of their 
1 Pfliigers Archiv, Vol. LV (1894), p. 525. 
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