1916-17.] Experiments and Observations on Crustacea. 55 
early was found to be approaching a new moult. Although no exact 
numerical statement can be made, I might express the result of these 
experiments in the following rough “rule”: “Death within 13 hours 
— old cuticle; survival beyond 22 hours — fresh cuticle.” It must be 
understood that the great proportion of deaths fell between these limits. 
The conclusion as to the importance of the moulting process is based on 
cases that fell beyond the limits. 
The longest survival-period accurately measured was 44-45 hours. In 
two other records it is stated that the animal lived “ more than 40 hours.” 
Numerous survival-periods between 30 and 40 hours were recorded. 
Another method was adopted to test the importance of moult in 
reference to the present question. Ligia moults in two stages. The 
cuticle of the posterior part of the body is first shed : about four days later 
the remaining cuticle is cast oft’. For some days before the first stage of 
moulting occurs the anterior part of the animal undergoes a conspicuous 
change of colour. In this way three stages in the immediate proximity of 
the actual moult are readily distinguished, viz. “just prior to moult,” 
“ between posterior and anterior moult,” and “just subsequent to anterior 
moult.” Successive sets of experiments were carried out on animals in 
these three stages. 
Just Prior to Moult. — Twenty-nine animals were immersed. The exact 
survival-periods of twenty-four of these were as follows : — 
Hours 
13-14 
14-15 
15-16 
16-17 
17-18 
18-19 
19-20 
20-21 
No. of Animals 
4 
3 
10 
2 
1 
1 
1 
2 
Three of the animals did not survive 13 hours. Two are recorded as having 
died “ before 18 hours.” 
Between Posterior and Anterior Moult . — Sixteen animals were im- 
mersed. Exact records were obtained in the case of nine, thus : — 
Hours ..... 
13-14 
14-15 
15-16 
17-18 
20-21 
No. of Animals 
1 
1 
5 
1 
1 
Three of the remainder did not survive 13 hours; four are recorded 
as having died “between 12 and 23 hours.” 
