ORIGIN OF MONSTERS 549 



Something, no doubt, did perish in the egg which Loeb describes 

 but it did so before the formation of the embryo. This early- 

 death of the part of the germ which was to form the part lack- 

 ing in the described egg is due to disintegration caused by the 

 noxiously low temperature. The parts of the germ which have 

 sur\dved have eventually developed — independently — into a head 

 fragment \Adth an eye, a clubby tail and a heart. The analogy 

 of this case with the 'solitary eye'-formations recorded in my 

 work is obAdous. 



That such cases are not due, as Loeb suggests, to the death 

 of a part of the already formed embiyo is further e\T.denced 

 very strongly by some eggs in which besides a complete, but 

 teratophthalmic embryo, there has developed independently 

 and at a great distance from the latter a small tissue fragment 

 with an eye. In the course of the experiments reported in this 

 paper three such eggs with '' isolated eyes" have been recorded^ 

 (cf. figs. 29, 42 and 43). 



One of these eggs (presented in figure 42) may now be briefly 

 described. The embryo is asymmetrically monophthalmic and 

 is also seen to lack all fins. No other defects could be observed 

 in toto. On the yolk-sac very near the distal end of the un- 

 usually large pericardial vesicle a small round tissue fragment 

 can be seen. Below it and at a ver^^ great distance from the 

 embryo a much larger tissue fragment with a well developed 

 eye can be observed. 



On microscopic examination of sections of the entire egg it 

 could be recognized that the smaller tissue fragment is a rudi- 

 mentary eye and that the interpretation of the larger tissue 

 fragment as an isolated eye is perfectly correct. 



The egg was cut into sections running transversely through 

 the embryo. In the most anterior sections through the embryo 

 (fig. 82) there can be seen on one side of the yolk the malformed 

 brain of the embry^^o with the anterior part of the eye, while on 

 the yolk's opposite side the smaller one of the isolated fragments 

 comes into view. This tissue fragment can, on careful examina- 



* More recent experiments (not yet published) have yielded a relatively great 

 number of eye-teratomata of both kinds (with and without an embryo). 



