ORIGIN OF MONSTERS. II 425 



A number of other duplicities have been recorded which also 

 are monstra et per defectum et per excessum (figs. 1 to 10). 

 Their genesis is, in all probability, due to the same factors that 

 have been assumed for the monsters above described. Thus 

 in the monster illustrated in figure 9, presenting double embryos 

 of strikingly unequal size and greatly deformed, one of the 

 ' twins' being amorphous, on microscopic examination indications 

 are found of chemical alteration, while in the duplicity of figure 

 6 in which an isolated head fragment with a well differentiated 

 eye (ascertained by microscopic examination) is observed at 

 a considerable distance from either of the 'twins', action of 

 osmotic pressure is apparent already on examination in toto, 

 if conclusions from analogous observations in invertebrates 

 (cf. for instance, Loeb, I.e.) be permitted. 



The smaller one of the double embryos of figure 8 when ex- 

 amined in sections is observed to lack the anterior part of the 

 head, the otic capsules appearing in the anterior-most sections. 

 This is one of the most conspicuous defects of this component 

 and, in my opinion, no error will be committed by assuming 

 that the factor which brought about the duplication of the orig- 

 inally single embryonic primordium (osmotic pressure) may have 

 contributed to the genesis of this and other defects by splitting 

 off the chemically incapacitated parts. In the other double 

 embryos recorded in our experiments which obviously are, at 

 the same time also monstra per defectum microscopic examina- 

 tion of sections would, undoubtedly, furnish indications of the 

 combined action of chemical alteration and osmotic pressure as 

 underlying the doubling of primordia and the origin of the 

 defects. 



THEORETICAL REMARKS AND CONCLUSIONS 



As pointed out repeatedly in the preceding pages no direct 

 evidence is available for this combined action of osmotic pres- 

 sure and chemical alteration. It may, therefore, seem desir- 

 able to inquire in how far their assumption is justified. 



Nearly all duplicities of our experiments have resulted from 

 the addition to sea-water (50 cc.) of a varied quantity (30 cc. 



