44 F. L. LANDACRE 
organs, finds confirmation in a comparison of the relative time of 
appearance of the placodes and taste buds in Lepidosteus and 
Ameiurus (Landacre, ’07). 
Approximately the same time, five days, intervenes between the 
fertilization of the eggs and the time of hatching in Lepidosteus 
and Ameiurus. If we compare the size at any given age, and rate 
of growth for any given period, Lepidosteus is found not only to 
be longer but to grow faster than Ameiurus. At the age of 113 
hours Ameiurus is 5.73 mm. long, while at the nearest correspond- 
ing age, 112 hours, Lepidosteus is 8 mm. long. Between the ages 
of 113 hours and 199 hours, Ameiurus increases 2.77 mm. in length, 
while Lepidosteus between the ages of 112 hours and 196, my 
nearest corresponding series, increases in length 5 mm.—a total 
difference in growth of 2.23 mm. in favor of Lepidosteus. Dur- 
ing this period Ameiurus increases 43.3 per cent while Lepidos- 
teus increases 62.5 per cent. 
If now we compare the more rapid rate of growth in Lepidos- 
teus with the time of appearance of preauditory placodes, the 
length of time intervening between the appearance of the first 
placode and the appearance of.the last, the time at which taste 
buds first appear, and lastly the total number of taste buds at 
any given age, we shall find all these processes beginning earlier 
and being completed earlier in Ameiurus, which is the slower 
growing form. 
The first epibranchial placode appears in Ameiurus preceding 
the 49-hour stage and the last placode appears at 105 hours. 
In Lepidosteus the first placode appears at 94 hours and the last 
at 191 hours. There is a difference of 45 hours between the time 
of appearance of these structures and a difference of 41 hours in 
the time intervening between the appearance of the first and the 
last placode, the placodes appearing earlier and consuming less 
time in their formation in Ameiurus which measured by length 
grows slower than Lepidosteus. The first taste buds appear in 
Lepidosteus at 191 hours, 97 hours after the appearance of 
the first placode while in Ameiurus the first taste buds appear at 
115 hours, 74 hours after the appearance of the first placode. 
So that here again the taste buds appear later and more time 
