STUDIES ON SEX IN CKEPIDULA 6 



MATERIAL AND METHOD 



The material was obtained from the Marine Biological Lab- 

 oratory at Woods Hole, Massachusetts, and work was carried 

 on there during the summer. Small compartments were ar- 

 ranged in one of the floating live-cars of the Laboratory, where 

 the hermit crabs with which the Crepidulas are associated could 

 be kept at about the same depth of water as that in which they 

 are normally found. They could thus be under constant ob- 

 servation, and the Crepidulas could be transferred from one shell 

 to another with some chance of their making a secure attach- 

 ment in the new situation. It was also found feasible to trans- 

 fer the Crepidulas to small glass dishes which were then put in 

 the small compartments of the live car or in the salt water 

 aquaria of the laboratory. 



During the winter, some hermit crabs with Crepidulas were 

 brought from the coast and kept in the salt water aquaria in the 

 vivarium of Princeton University, where they lived fairly well, 

 some for over a year. This situation did not prove so favorable, 

 however, as the more nearly normal one in the live-car at Woods 

 Hole. 



In killing the specimens, a number of fixing fluids were used, 

 of which the most favorable for general work was Bouin's picro- 

 formol-acetic. This mixture will decalcify the shells as well as 

 harden the tissues, and thereby avoid the distortion of the or- 

 gans often caused by pulling the Crepidulas from their shells. 

 For some of the finer cytological work Flemming's stronger mix- 

 ture was used, and occasionally gave beautiful preparations, but 

 it was very unreliable. Fixation with Flemming to which urea 

 had been added, fixation at low temperatures, or in the dark, 

 and other recent methods of technique with osmic acid fixing 

 fluids, did not insure good preparations. 



The results of the study are drawn from over a thousand slides, 

 each containing sections of the gonad and goniduct of one indi- 

 vidual Crepidula. Material was put up during every month of 

 the year, with a view to observing any seasonal differences in 

 the sexual condition. 



