316 \\". C. ALLEE AND J. F. SCHUETT. 



with which animals seldom or never come in contact in nature. 

 Chemically clean glass dishes, filled with conductivity water given 

 the proper osmotic value by the addition of chemically pure salts, 

 and supplied with the optimal quantities of pure food do not fur- 

 nish an optimum habitat for many animals, and it does not neces- 

 sarily follow that the relations shown under such conditions would 

 be duplicated in nature. There is, however, enough reason for 

 thinking that similar relations may obtain in nature to justify 

 further investigations. 



Regardless of the protective mechanism, the fact that under 

 certain conditions, masses of animals may have greater survival 

 value for their components than would be the case if all were 

 isolated, is of decided and general biological significance. In 

 large bodies of water such aggregations might condition the water 

 immediately around them, and in small bays where conditions be- 

 come more pond-like, or in the more restricted area under small 

 rocks, such conditioned water might have considerable perma- 

 nence. In tide-pools, or in small streamside pools, the community 

 auto-protection could easily have marked survival value. Even 

 if it should appear that the only protection furnished is the dis- 

 tribution of the toxic agent among so many animals that none re- 

 ceive a lethal dose, the older conception that crowding is always 

 a menace, hibernation and breeding season sometimes exceptecl, 

 must be revised ; and the indicated revision allows a better under- 

 standing of the persistence and probable significance of animal 

 aggregations of a low level of integration. 



REFERENCES. 

 Alice, W. C. 



'26 Studies in Animal Aggregations: Causes and Effects of Bunching in Land 

 Isopods. Jour. Exp. Zool., 45: 255-277. 



'27 Animal Aggregations. Quarteily Rev. Biol., 2: 367-398. Bibliography. 



'270 Studies in Animal Aggregations: .Some Physiological Effects of Aggrega- 

 tion in the Brittle Starfish, Ophioderrna brevispina. Jour. Exp. Zool., 

 48: No. 2. 

 Bresslau, E. 



'22 Die Ausscheidung entgiftender Schutzstoffe bei Ziliaten. Ber. Deutsch. 

 Yer. Mikrobiol. Centrabl. f. Bakteriol. u. Parasit. I. Abt. Orig. 89: 

 87-90. 



'24 Die Ausscheidung von Schutzstoffen bei einzelligen Lebenwesen. Ber. d. 



Senckenberg. Naturf. Gesellsch. 54: 49-66. 

 Drzewina, Anna et Georges Bohn. 



