DYNAMICS^ — MORPHOGENESIS AND INHERITANCE 425 



changes. The original cephahc lobes are resorbed or atrophy 

 and new ones develop in normal position. In figure 25 the old 

 disappearing lobes are indicated near the tip of the head. In 

 the stage figured here the lobes as actual outgrowths have already 

 disappeared, the two areas indicated in the figure representing 

 the unpigmented sensory areas at the base of each lobe. The 

 eye changes consist either in the development of two complete 

 eyes in addition to the median eye (figs. 25, 26) or in various de- 

 grees of teratophthalmia (figs. 27, 28), and the median regions 

 of the ganglia also develop more or less completely. Such trans- 

 formation has been observed repeatedly in all its stages. It 

 occurs chiefly in the less extreme teratomorphic types, such as 

 figures 5 and 6, the more extreme types (figs. 7, 8) being in most 

 cases permanent. 



As pointed out above, the teratomorphic head results from 

 inhibition of the median regions to a certain degree, and it is 

 evident that the secondary transformation of such heads repre- 

 sents more or less complete acclimation to, or recovery from, the 

 earlier differential inhibition; that is, the median regions at first 

 inhibited, later undergo more or less complete development. 



Secondary transformation of anophthalmic heads. Heads which 

 develop at first as anophthalmic heads of ordinary form (figs 

 10, 11) very often show secondary elongation, particularly of the 

 median region (figs. 29 to 31), and in some cases a median cepha- 

 lic lobe develops at the tip (fig. 32) and occasionally after two or 

 three weeks a single median eye (fig. 33) ; i.e., the anophthalmic 

 may in some cases become secondarily a teratomorphic head. 

 Here again it is evident that the secondary transformation re- 

 sults from growth and often hypertrophy of those head regions 

 which were at first most inhibited. 



Secondary transformation of acephalic forms. Such transforma- 

 tion is also of very frequent occurrence in acclimation to, 

 or recovery from, inhibiting factors. Pieces which remain 

 acephalic indefinitely under the inhibiting conditions may 

 develop anophthalmic, or in some cases teratomorphic, and 

 occasionally even teratophthalmic heads when acclimation or 

 recovery occurs. Acchmation usually results in forms like 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 33, NO. 2 



