DEPARTMENT OF MARINE BIOLOGY. 199 



The same state of affairs, only in a still more exaggerated form, obtains in 

 the Cerion casahlancce colony, for sheep and pigs have been introduced in the 

 region occupied by this species. The larger vegetation has been cut down 

 with the ax in order to improve the habitat for grass culture, and the smaller 

 vegetation, grasses and shrubs, are being rapidly eliminated by the grazing 

 sheep, while the mollusks themselves are sought by the pigs. If this state 

 of affairs continues this colony will probably disappear altogether, extensive 

 as it was in 1912. The necessary specimens for our experiments, however, 

 were secured by a dihgent and exhaustive search. In addition to the breed- 

 ing material, we also secured a set of adults of both Cerion viaregis and Cerion 

 casahlancoe for comparison with the material gathered in 1912. 



During our trip to the Bahamas, gatherings of cerions were made from every 

 colony discovered along the east-central shore of Andros and the banks of 

 South and Middle Bights. While waiting for transportation to Miami from 

 Nassau, we put in use the Bull Pup, a small motor-launch that we carried 

 to the Bahamas with us, and thoroughly explored all the cays lying off 

 southwestern New Providence for cerions, and we believe that we charted 

 every colony on those islands and the adjacent shores of the mainland. 

 These gatherings, embracing more than 20,000 specimens, may serve as a 

 check series with which future gatherings from the same colonies may be 

 compared. 



We returned to Miami June 3; on the 4th we sailed south for the Tortugas, 

 our first stop being on the First Ragged Key north of Sands Key, which by 

 filUng in with dredges has been rendered many times its former size, and the 

 region occupied by our cerion colony has been completely covered with 

 dredged-up ocean bottom, so that this colony, we may say, is completely 

 buried. 



The Second Ragged Key north of Sands Key appears to have been pretty 

 well swept over by the high water occasioned by the hurricane, and only a 

 few specimens of our cerion colony were observed. However, an exhaustive 

 search was not made, as we wished merely to establish at this time the approxi- 

 mate state of the colony. The mosquitoes, too, this year were about the worst 

 that we have encountered on the east coast. 



The planting on the east side of Sands Key was again visited, but no speci- 

 mens were observed in the rank vegetation which covers the place. 



The Indian Key colony seems to have been saved by the rank growth of 

 sisal and other vegetation, but no specimens were seen on Tea Table Key. 



I was unable to find any cerions on Duck Key. 



On Bahia Honda Key the hurricane has made decided changes. The ditch 

 along which our planting was made now separates the outer portion of the key 

 almost into a distinct island. A lake of considerable size occupies the place 

 where our planting was located and none of the introduced cerions was seen. 



The hybrid colony on Newfound Harbor Key, in which our greatest interest 

 centered, strangely enough seems to have suffered less than any other. Not- 

 withstanding the location of this colony was rather low, it was not destroyed, 

 as was feared. Evidently the rain preceding the hurricane had caused 

 the cerions to take to the ground, as they usually do for foraging purposes 

 under such conditions, and the dense mats of grass here had kept them from 

 being swept away by the floods that must have passed over them; yet many 

 dead specimens were found, which were taken for record purposes. 



At Key West a gathering of adolescent Cerion incanum was made near the 

 aquarium site for our breeding experiments. 



The colony at Boca Grande has suffered much through fire and storm, yet 

 specimens could be easily seen. 



