416 E. I. WERBER 



that on examination of sections of some double monsters result- 

 ing from these experiments conditions are found which suggest 

 that the duplication of the embryonic anlage was due to dis- 

 sociation by the combined action of both chemical alteration 

 and osmotic pressure (blastolysis) . 



The following cases may serve as illustrative examples of the 

 apparent effects of such action. 



In figure 11 is presented a 'parasitic' duplicity which in toto 

 made the impression of a greatly deformed craniothoracopagus. 

 Examination of sections practically confirms this diagnosis, 

 except for the incompleteness in the duplication of the head. 



The transverse sections (6 m in thickness) being somewhat 

 oblique, those farthest anteriorly contain more of the right than 

 of the left side of the duplicity. A large lens is noted in them, 

 an olfactory pit and a distorted, unilobed fore-brain. The 

 lens (but no eye on this side) was observed already in toto and 

 was mistaken for a 'free lens.' In further sections, however, 

 there comes into view in apposition to it a very small optic 

 cup (fig. 14). A very small, lens-like body (I) can also be ob- 

 served in several sections at this level between the ill-differ- 

 entiated optic cup and the large lens. On following the sec- 

 tions posteriorly the eye of the left side gradually comes into 

 view (figs. 14 and 15), while the optic cup of the right side be- 

 comes more and more elongate and is noted still to be in direct 

 connection with the brain, no optic stalk having been formed. 

 In sections still further posteriorly this eye is very plainly seen 

 to be broken up (dissociated) into several parts — one of which 

 at the base of the brain with which it is connected, has made a 

 feeble attempt towards differentiation of the retinal layers, 



Fig. 1 (a and b) Anterior and posterior views of slightly conjoined twins, 

 A the larger, B the smaller one, From acetone solution (40 cc. gram-molecular to 

 50 cc. of sea-water), 19 days old, h., heart, pc, pericardial vesicle. 



Fig. 2 (a and b) Two views of slightly conjoined double embryo, A the larg- 

 er, B the smaller one. From butyric acid solution (10 cc. of a 1/16 gram-molec- 

 ular solution added to 50 cc. of sea-water), 13 days old, pc, pericardial vesicle. 



Fig. 3 From acetone solution (35 cc. gram-molecular tooOcc. of sea-water), 

 14 days old. 



Fig. 4 From acetone solution (35 cc. gram-molecular to 50 cc. of sea-water), 

 14 days old. 



