( G01 ) 

 SUMMARY 



OF CURRENT RESEARCHES RELATING TO 



ZOOLOGY AND BOTANY 



(principally Invertebrate* and Cryptogamia), 



MICROSCOPY, &c, 



INCLUDING ORIGINAL COMMUNICATIONS FROM FELLOWS AND OTHERS; 



ZOOLOGY. 



A. GENERAL, including Embryology and Histology 

 of the Vertebrata. 



Symbiosis of Dissimilar Organisms.! — G. Klebs, starting with the 

 principle that the life of every organism is necessarily bound up with 

 the life of others, directs attention to some of the general conclusions 

 derivable from a study of symbiosis. 



A great step in advance was made when P. J. van Beneden dis- 

 tinguished commensalists and mutualists from true parasites, even 

 though these divisions and their definition may require some amend- 

 ment. When one organism lives in or on another, this relation may be 

 due to one of two sets of causes ; we have cases in which only one of 

 the organisms is more or less compelled to be associated for some 

 part of its life with another ; here we have the proper relation of 

 host and guest, or one-sided adaptation. In other cases it is necessary, 

 that the two symbiosists should live together, and here we have 

 mutual adaptation, though one may be more dependent on its fellow 

 than the other on it. 



The author in what follows confines himself to the former set of 

 cases, pointing out that the essential part of the relation is taken by the 

 organism which seeks out the other, often larger, and often also more 

 highly organized, for the purpose of fulfilling its own mode of life. 

 Any one who has examined life in a pool or in the sea knows that 

 almost every large organism, be it plant or animal, is covered with a 

 number of smaller ones ; this is the simplest case of symbiosis : 

 smaller organisms make use of the surface of the larger one ; thus 

 alga? will be found covered with diatoms ; every tree on land is beset 

 with algae, lichens, and mosses, and often there is a definite relation 

 between them and the kind of tree on which they live. Various plants, 



* The Society are not to be considered responsible for the views of the 

 authors of the papers referred to, nor for the manner in which those views 

 may be expressed, the maiu object of this part of the Journal being to present a 

 summary of the papers as actually published, so as to provide the Fellows with 

 a guide to the additions made from time to time to the Library. Objections and 

 corrections should therefore, for the most part, be addressed to the authors. 

 (The Society are not intended to be denoted by the editorial " we.") 



t Biol. Centralbl., ii. (1882) pp. 289-99. 



