64 



C. M. CHILD 



with two eyes and two lateral cephalic lobes, as in figure 1. In 

 the teratophthalmic form the eyes are either partially or wholly 

 united or unequal in size or abnormally placed. The terato- 

 morphic form has a single eye in the median line and the cephalic 

 lobes appear on the front of the head and may be partially or 

 completely united in the median line. In the anopththalmic 

 form an anterior outgrowth is present, containing a small abnor- 

 mal ganglionic mass, but eyes do not appear. And finally, the 

 headless form shows no anterior outgrowth except closure of 

 the wound. 



The increase in head-frequency in the short pieces is evident 

 from table 1. In Lot I, 80 per cent remain headless and only 

 8 per cent give rise to heads with eyes of any kind and none are 



normal. But Lot II shows that after 3 to 4 hours the anterior 

 ends of the long pieces have been determined as heads to such an 

 extent that their isolation as parts of short pieces prevents head- 

 formation completely in only 28 per cent, while 24 per cent are 

 anophthalmic and the rest form heads with eyes, 4 per cent 

 normal, 32 per cent teratophthalmic and 4 per cent teratomorphic. 

 In Lot III, where the short pieces were cut off after 7 to 8 hours 

 as parts of the long pieces, only 12 per cent remain headless and 28 

 per cent are normal and 60 per cent teratophthalmic. In Lot IV, 

 after eighteen hours, 76 per cent are normal and 16 teratophthal- 

 mic, and in Lot V, after twenty-four hours, 80 per cent are normal. 

 After 18 hours the head is so fixedly determined in practically 

 all cases that isolation of the head-forming region as part of a 

 short piece cannot prevent head-formation. The approach in 



