164 CARNEGIE INSTITUTION OF WASHINGTON. 



REPORTS OF INVESTIGATORS. 

 Breeding Experiments with Cerions, by Paul Bartsch. 



Dr. Bartsch continued his cerion studies at the Laboratory from May 7 

 to May 23. 



A careful examination of the hybrid cerion colony on Newfound Harbor 

 Key was made and many dead specimens were gathered and carried to 

 Washington for detailed study. This colony continues to be of great interest 

 on account of the extreme diversity of form, sculpture, and markings produced 

 by the crossing of Cerion viaregis with Cerion incanum. 



Thanks to the good offices of the Navy Department, a naval seaplane, 

 under the command of Lieutenant Noel Davis and Lieutenant L. F. Noble, 

 was detailed to Dr. Bartsch for use in examining the Florida Keys. By the 

 use of this machine it was possible to examine all the keys lying between 

 Miami and the Tortugas, including those in the Bay of Florida, west to Cape 

 Sable, and to mark on charts all grass plots on the keys within this region. 

 It is in such grassy meadows that the native cerions make their home. Dr. 

 Bartsch has for a number of years studied the extent of distribution of the 

 native species. This, by means of the boat facihties, has proved a rather 

 trying task, because it was found necessary to break through mosquito in- 

 fested mangrove fringes to reach the interior of the keys, where the grassy 

 plots usually occur, and in the larger keys many such excursions were made 

 necessary in order not to overlook any possible colony. By means of the 

 reconnaissance work done this year, it will be easy to go directly to the places 

 where meadows are now known to exist and make the necessary examination 

 for the mollusks in question. It is beUeved that about a year's work was 

 saved by the use of the seaplane. 



Incidentally it was found that the milky, oozy condition characteristic of 

 the waters of Florida Bay for some years has disappeared, and that adequate 

 vegetation and animal life are rapidly reestablishing themselves in the region. 

 This is interesting, because the same state of changed affairs was noted on 

 the west coast of Andros, in the Bahamas, last year. It seems to indicate 

 that the partial depletion of the Florida continental-shelf fauna and flora 

 was not due to local conditions, but to widespread oceanographic factors. A 

 comparison of the fauna and flora now establishing itself, with that of the 

 past, promises an unusually fine field for a study in distribution. 



At the Tortugas, all the cerion colonies were examined and measurements 

 and photographs were taken of 43 of the first generation of Florida-grown 

 Cerion uva, the parents of which came from Curagao. 



It was found that the individual pairs of specimens planted in the cages 

 last year and also the larger aggregations planted in cages had all died. 

 Experimenting during his stay at the Tortugas led Dr. Bartsch to believe 

 that this was due to the fact that the cages had been covered with fine-meshed 

 wire, this screening preventing the dew from reaching the interior of the 

 cages, and it is beheved that the deaths were due, therefore, to a want of 

 moisture, for as a rule there is a heavy dew on Loggerhead Key at night, the 

 time at which cerions are active. 



For that reason new plantings were made and a narrow fringe of wire only 

 was placed around the edge of the top of the cages to prevent the organisms 



