588 SCIENTIFIC RECORD FOR 1884. 



of tlie reservoirs. The feeble curreDt.s produced by each can only 

 bring within its reach the floating provision frnni a ver}' limited area ; 

 the volume of water poured through these gates brings to them a rich 

 supply, and the numbers and variety of these organisms increase in pro- 

 portion. Of the fixed forms were seen amongst the bryozoa, besides one 

 or more undetermined si)ecies of Plumatella, PeciinateUa magnijica, and 

 Urnatella gracilis of Leidy, and the newly described Paludicclla erecta. 

 Attached to these were vorticella), epistilis, and steutors innumerable; 

 Pyxicola and Acineta^ rotifers of various names, including prominently 

 Limnias and other probably undescribed forms among the melicertidae. 

 Very abundant among these was the interesting chaetobranch annelid, 

 Manuyiinlda speciosa Leid\', which has of late been frequently noticed 

 in this vicinity, and the wonderfully marine-looking hydroid Cordylo- 

 pliora lacustris. This last was particularly abundant around the south- 

 east outlet, its stems forming a complete matting over many yards of 

 surface, commingled with bryozoa and sponges in intricate confusion." 

 {Proc. Acad. Nat Sc. PMla., 1884, pp. 217-219.) 



Symbiosis of Hermit Crab and Sea-Anemone. — The subject of Sym- 

 biosis, or the association for mutual benefit of different animals, or, 

 may be, of an animal and a plant even, has of late been attracting much 

 attention. The name was first suggested by the French botanist, De 

 Bary, in connection with certain phenomena of the vegetable world. 

 The associates come together and associate "like two partners in a well 

 regulated business concern, co-operating in the work of life, taking part 

 in all its toils and troubles, and honorably sharing the common profits." 

 The symbiotic relationship of one of the hermit crabs and a sea-anemone 

 [Adamsia paUiata) has been studied in the Naples aquarium by Pro- 

 fessor Hertwig. The sea-anemone, a beautiful species, " attaches itself 

 to the roof of the common abode in such a position that its mouth and 

 prehensile apparatus are always turned toward the head of its associ- 

 ate. It is thus enabled to join in all the expeditions of the restless 

 hermit crab and conveniently share in the common plunder. In return 

 for this service the anemone i)rotects its companion from his many 

 enemies by means of the numerous long threads which it shoots out at 

 the least alarm, and which are provided with millions of capsules 

 charged with a stinging acid like that of the common nettle. So close 

 is the compact entered into by the two partners that both have become 

 indispensable to each other," and, " if the crab be removed from his 

 house, and this be stopped up so as to prevent his re entering it, he will 

 cast about for another shell, and never stop until his old associate is 

 also transferred to their new abode." Many similar cases of symbiosis 

 of actinians and decapod crustaceans are now known, and the relation- 

 ship is probably as intimate in almost all cases as the one studied. 

 (Am. Nat., x\iu. pp. 83, 81.) 



