538 



E. I. WERBER 



there being no division into a right and left lobe. This is evi- 

 denced very plainly by figure 52, which is a transverse section of 

 a synophthalmic embryo, as well as by the cross sections of the 

 Cyclopean embryos illustrated in figures 63, 66 and 70. The mid- 

 brain and hind-brain are mostly bilobed and otherwise symmetric. 

 Sometimes, however, and usually only in cases of perfect cyclopia, 

 the single unilobed condition may be found to obtain also in the 

 mid-brain (cf. fig. 48, p. 513, also figs. 65 and 67) and even in 

 the hind-brain (fig. 71). 



Fig. 52 Camera lucida drawing of a transverse section through the eye region 

 of a synophthalmic embryo from acetone solution (35 cc. gram molec. to 50 cc. 

 sea-water) thirty-two days old. fbr., fore-brain; oe., oedema; e.oe., extracerebral 

 oedema;/., fibrin; m, mandible. X 100. 



An important clue to the genesis of this disturbance in the 

 symmetry of the forebrain (and rarely also of the mid-brain) is 

 given by the size of the latter. In transverse sections it is often 

 much smaller in area than the synophthalmic or cyclopean eye, 

 as a glance at text-figures 48 and 52 and figures 63, 65, 66, 67 

 and 70 will convince. This indicates clearly that something is 

 lacking in such brains. In other words, we are here dealing with 

 defects. They are undoubtedly the same defects which resulted 

 in the deformities of the eyes of these embryos, and are due to 

 blastolytic elimination of a Svedge' of tissue from the anterior 



