MODIFICATION OF DEVELOPMENT IN THE FROG 489 
posterior ends. Except for this apparent lack of anteroposterior dif- 
ferentiation, they remind one just a little of a teleost egg. One of these 
peculiar embryos was isolated (fig. 50) because it had, at the time, the 
appearance of being bipolar, i.e., possessing either two heads or two 
tails, one at either end of the ‘embryonic area.’ Several days later, 
however, it developed into an almost anencephalic embryo with a more 
or less characteristic tail bud (fig. 51). 
Us, 
ee 
50 
48 
4 f oe —a 
epee fs SE * = > 
ihe Cl Fe fe : Senn = 
a eS STEEN 
te tex HY if af Tee a 
id 
Ped Sf 5 3 E <I 
Aarts lees “nce Pe 
oe fin =a here 2a) 
iB Po yo Sd eee ae 4 
se he ae peat neice : 
Me MeLioes ess aa) 
aOR i esecae Sarae 
Sie sy < PADS 2 
aN Piso Sear a 
x peterestee = 
ee ates) ‘4 oi 
Seep 
ae tars ee 5] 
Figs. 47 to 51 Differential inhibition. m/5 LiCl. Eggs late cleavage stage 
when placed in the solution. Treatments: 47, 3 hours in LiCl + 79 hours in 
water. Lateral view (anterior end at top) of an extreme type showing little 
regional differentiation. 48, 49, 3 hours in LiCl + 103 hours in water. Shows 
some recovery. 90, 51, see text, page 489. Exp. IV 58. o.p., olfactory pit; v.s., 
ventral sucker. 
oO 
kK—7m— 
Lot D. (a) 5 hours in LiCl, plus 4 hours in water. The eggs are 
in much the same condition as those in lot B (a). 
(b) 5 hours in LiCl, plus 47 hours in water. Large yolk 
plug stages or equatorial gastrulae and in many cases showing a second- 
ary invagination above the equatorial blastopore. An egg of this sort 
was figured (fig. 18) in the previous report. 
