THE LARVAL CASE OF I'LATYPII VLAX. 235 



of the case the original pile of sand grains has been attached to 

 its posterior end and may be dragged around by the larva ; it is 

 however finally cut off and remains at the bottom of the aquarium. 

 Whether or not the construction is similar in the natural habitat 

 of the larvae we do not know. 



CASES CUT LONGITUDINALLY FROM END TO END. 



Without removing the larva.- the cases were cut with scissors 

 from end to end and on different surfaces. It was necessary to 

 cut the cases slowly avoiding the largest sand grains and taking 

 care not to injure the larva-. 



1. The cases of three larva; were cut, one dorsally, one ven- 

 trally, and the third along the lateral surface. The following 

 day the laterally cut one had glued the cut surfaces together in 

 the anterior region ; the other two had not been repaired. 



2. The experiment was repeated with three more larvae and 

 at the end of twenty-four hours all had glued, anteriorly, the 

 cut edges together for one third the distance. 



3. The case was cut ventrally in one larva and on the follow- 

 ing day it had been repaired the same as above. 



4. A larva with case cut dorsally gave the same result. 



5. On the twenty-sixth of the month a case was cut dorsally 

 and the larva removed from it ; the following day it had returned 

 to its case and cemented the edges at the anterior end for about 

 one quarter of the distance. Twenty-eighth, the larva had cut 

 out a notch at the anterior end, at terminus of original cut, and 

 built in with new sand. Twenty-ninth, had added a few sand 

 grains to posterior edge of shell. First of following month, had 

 added a band, two grains wide, at the anterior margin. 



6. On the twenty-fifth a case was cut dorsally which by the 

 following day had been repaired at the anterior end for about 

 one third its length. Twenty-eighth, case cut again in the same 

 plate. Twenty-ninth, no repair. Thirtieth, edges glued a little 

 at anterior end and two rows of sand grains added to this margin. 

 Thirty-first, same. First, cut again. Second, glued anterior 

 third of distance and added from four to five more rows of sand 

 at this end ; cut again in same place. Third, again glued at 



