No. 398.] SPECIFIC GRAVITY OF ANIMALS. 105 
2. That the specific gravity decreases with the increase in 
volume, as one would expect if the increased volume is due to 
imbibition of water. 
3. That the percentage of dry weight continues to decrease 
even after the absolute dry weight, owing to the acquisition of 
food from without, begins to increase. A similar set of results 
expressed in the form of a curve is given by Davenport (97-99, 
p. 285). 
In the case of the toad series growth was so slow that for 
the greater lengths (8 mm. and upwards) I took toads from out 
of doors. All had reached the feeding stage, the intestines of 
all being full, and since the conditions were the same and the 
lengths not greatly, different, their specific 'gravities were 
essentially the same. 
The preceding table was based on developing forms of 
Amphibians. I give also for comparison the relation which 
exists between dry weight and total weight in a few individuals 
of essentially adult fish. 
TABLE VII. 
NuMBER OF | LENGT Live Dry Per CENT 
INDIVIDUALS.|  (mm.) WEIGHT. | WEIGHT. Dry WEIGHT. 
Fundulus ., 2 32 2090 :0454 21.7 
Fundulus I 35 .2780 0622 22.6 
Fundulus 2 44 6336 -1490 23.6 
Gasterosteus I - 3o -1449 0358 23-4 
Gasterosteus I 60 1.4041 3179 28.6 
These fish were dried ten days. The larger the fish is, the 
greater the per cent of dry weight. 
As one would expect, the armored stickleback has a greater 
per cent dry weight than Fundulus. 
III. 
The last section of the paper has reference to the location of 
the imbibed water in the tissues of the tadpole. I give three 
