128 REPORTS OP INVESTIGATIONS AND PROJECTS. 



tance with snail-like movements. But soon the tentacles catch hold of the 

 substratum on all sides, and with considerable writhing the anemone loosens 

 the base and walks on its tentacles in an inverted position to a new place, 

 where it rights and attaches itself. Small crabs live in the cavities with the 

 anemones and crawl over them with impunity, as the anemones are not 

 strong enough to swallow the crabs. It is not probable that the fronds serve 

 as a protective function, but they may serve as lures for catching prey. 



Stoichactis hclianthiis. — Another reef anemone, Stoichactis helianthus, was 

 found to crawl with snail-like movements similar to Metridium. It reacts 

 negatively to light falling on its base. 



STUDIES OF CRUSTACEA. 



Synalpheus Icsvimanus longicarpus Herrick lives in the cavities of the 

 loggerhead sponge. The animals occur in such numbers that 200 c. c. of 

 them could be obtained from a sponge 2.5 feet in diameter. In the same 

 sponge would be found 4 or 5 small Amphipods and about 6 to 12 specimens 

 of an undetermined Potoniid. The /Vmphipods seemed to go into small cavi- 

 ties beyond the reach of the Alphei, but the Potoniids were similar in size 

 and shape to the Alphei, and had very similar habits in so far as these could 

 be investigated. Whereas Alpheus has the first pair of thoracic legs greatly 

 and as3mimetrically developed, the same is true of the second pair of thoracic 

 legs of the Potoniid. In both animals the largest claw can be closed with 

 such rapidity and force as to produce a loud snapping sound (this is true of 

 the smaller claw also in the Potoniid) . The animals will eat crab-meat, but 

 as only 2 or 3 out of about 1,000 were seen to come outside of the sponge (at 

 night) it is probable that the large claw is for defense, and that the animal 

 feeds on the sponge or food brought in by the currents in the sponge. The 

 .striking similarity of these two species of widely separated genera might lead 

 one to suspect a case of protective mimicry. As a matter of fact, the Alphei 

 are not always very friendly to one another, and as the Potoniids are equally 

 well, and possibly better, armed and can not be assailed by great numbers in 

 the narrow cavities of the sponge, it seems hardly necessary for them to de- 

 ceive the Alphei in order to exist. I think we have here a case of conver- 

 gence in structure which has caused the animals to become adapted to the 

 same mode of life. 



Preliminary Report on Bryosoa of the Tortiigas, by Raymond C. Osburn, 



Cohifu bia University. 



It was the privilege of the writer to spend the greater part of the month of 

 June, T908, at the Tortugas Laboratory, collecting the Bryozoa of the region. 

 No report has ever been made upon shallow-water collections from the south- 

 ern part of the Atlantic coast of North America, although Smitt's excellent 

 paper on the Floridian Bryozoa collected by Pourtales (Kongl. Svensks 

 Vetenskaps-Akd. Handl., 1872-3), probably covers the deeper-water forms 

 fairly well. For these reasons my attention was directed to shore and shal- 

 low-water collecting, as promising the most interesting results. 



The piles of the U. S. naval docks at Garden Key, the moat surrounding 

 old Fort Jefferson on the same key, and the drift on the shore of Loggerhead 

 Key were carefully worked. Material was collected at low tide on the reefs. 



