36 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 
The young lobsters, after hatching, shed their skin three times 
during as many weeks, and following each moult there is a marked 
change in the structure as well as in the size of the animals.* 
Accordingly, it is convenient to designate the young immediately 
after hatching as belonging to the “ first stage ;” after they have 
moulted once, as belonging to the “ second stage,” and soon. The 
surest and quickest means of distinguishing the different stages is 
by the appendages along the under side of the abdomen (tail). In 
the first stage there are none; in the second stage several pairs of 
swimmerets are present; in the third stage appendages appear 
upon the end segment of the tail. The fourth stage is so different 
from the preceding ones that no difficulty is ever experienced in 
distinguishing it. 
The time required to reach the fourth stage varies greatly ac- 
cording to the temperature of the water, and perhaps according 
to other conditions. At Wickford this period varied from nine to 
sixteen days, and became shorter as the temperature became 
higher. At Wood’s Hole the development was very much slower, 
and the period was nearly twice as long as at Wickford. 
A great deal of attention was given to the general habits of the 
fry during the first three stages, for obviously the success of the 
experiments depends in a large measure upon understanding them. 
From the time they are hatched until they reach the fourth stage 
they are essentially swimming animals, and are in no way adapted 
for living on the bottom or in contact with any solid substance. 
They are constantly in motion; in moments of apparent rest the 
motion of the swimmerets prevents them from sinking, and for the 
greater part of the time they are swimming around or executing 
absurd jerking movements*by sudden strokes of the tail. Only 
slightly do they direct their movements toward particular objects 
or places, but they are carried by the current in the direction of 
least resistance. Their constant aimless activity tends to keep 
them suspended in the water and occasionally brings them into 
*F, H. Herrick,“*‘ The American Lobster:;” Bulletin of the United States Fish Commission 
for 1895; and Report of Rhode Island Fish Commission for 1900. 
