THE LARVAL CASE OF PLATYPHVLAX. 243 



2. Reentered case at the anterior end, the regular method, 

 but in reversing stuck fast and died. 



3. Returned to old case five times out of seven trials. Built 

 12.5 mm. in eleven days. Average i.i mm. per day. 



4. Out of eight trials returned to its old case twice and to that 

 of larger larva once. Built five new cases in thirteen days with 

 a total length of 42 mm. Average 3.23 mm. per day. 



5. Did not return to its old case. Out of eight trials lasting 

 thirteen days a new case was built each time but one. Daily 

 average 4 mm. 



6. In six trials built a new case each time then occupied case 

 of larger larva twice, the last time adding a new part of smaller 

 diameter to the shell. In twelve days built 42 mm. of new case. 

 Average 3.5 mm. per day. 



7. Out of six trials returned to old case five times, building 

 only 5 mm. of new material. Went without case for two days 

 during which time the old case was occupied by another larva. 

 Daily average of new case construction only 0.38 mm. 



8. In eight trials a larva returned once to its own case, three 

 times to that of a larger larva, and four times built new cases ; 

 23 mm. of new cases were built in fourteen days. Daily average 

 1.64 mm. 



9. Did not return at all to old case but built, in fourteen days, 

 a total of 65 mm. Average daily construction 4.64 mm. 



10. November 7, took a larva out of its case and it immediately 

 crawled in again at the anterior end. Eighth, had assumed 

 proper position in case and added new ring of sand grains at 

 anterior end. Removed again from case but it reentered as 

 before. On the ninth, tenth and eleventh, the larva was removed 

 from its case but each time time reentered and added a little new 

 material to the anterior end, 3 mm. in all. Twelfth, removed 

 from case but did not again return and not until the sixteenth 

 was a new case constructed, at which time it was 10 mm. long. 

 Seventeenth, case 15 mm. in length. Eighteenth, case 16.5 mm. 

 long ; removed larva from it. Nineteenth, had constructed a 

 new case which was 1 1 mm. long. Twenty-first, new case had 

 2 mm. more added ; removed the larva. Twenty-second, another 

 new case 7 mm. long had been built ; again removed the larva. 



