ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 21 



same type as the hypophysis, and that their function in all probalility 

 is the regulation of the amount of sugar in the blood. 



c. General. 



Symbiosis.* — Dr. F. Fedde shows, in an interesting lecture, that 

 intimate partnerships or vital co-operations between organisms are of 

 frequent occurrence. He uses the term symbiosis widely, to include 

 commensalism and antagonistic symbiosis (= parasitism), as well as 

 that intimate internal co-operation illustrated by Radiolarians and their 

 partner alga3, to which, as it seems to us, there is good reason for re- 

 stricting the term. He distinguishes what maybe called, zoo-symbiosis, 

 phyto-symbiosis, and zoo-phyto-symbiosis. It is interesting to com- 

 pare this lecture with a well-known one by Oscar Hertwig, for the com- 

 parison shows that many fresh illustrations have come to light. 



Genesis of Mid-Pacific Faunas.f — Dr. H. A. Pilsbry discusses the 

 hypothesis of a late palaeozoic or early mesozoic raid-Pacific continent, 

 upon the sunken heights of which the present island masses, volcanic 

 •or coral, have been superposed. The hypothesis is advanced to account 

 for the constitution of Polynesian land-snail faunas, which are shown 

 to be : — (1) nearly homogeneous over vast areas ; (2) composed of ancient 

 types, with no admixture of the great series of modern families ; and 

 (3) not derivable from any tertiary or modern continental fauna or 

 faunas in the sense in which Atlantic island faunas have been derived. 

 The molluscs, laud and marine, supply no evidence that this Pacific con- 

 tinent was ever connected with or faunally affected by America (North 

 or South), but are against any such connection. 



Power of Flight in Vertebrates.^:— Prof. L. Doderlein notes that if 

 "the known species of animals be estimated at 420,000, then some 62 p.c. 

 of these possess the power of flight in some form. If from the total 

 there be subtracted such groups as the Protozoa, Ccelentera, &c, where 

 the method of life excludes the possibility of flying organs, the propor- 

 tion of flying animals in the remaining terrestrial forms is so large as 

 to lead to the conclusion that flying is the ideal method of locomotion 

 for land animals, and gives the possessors of the power an enormous 

 advantage in the struggle for existence. In Vertebrates the flying- 

 organs may be divided into two sets, true wings which can produce 

 movements of the body in air without the aid of a fixed starting-point, 

 and parachutes which cannot be flapped, do not produce independent 

 movements, but can be utilised in supporting the body during leaping. 

 Such parachutes are found in two genera of fishes, in a frog, in two 

 groups of lizards, aud in four groups of mammals, and are theoretically 

 capable of being used in two ways. They may be used in taking leaps 

 from the ground, a possible use of which there is no example in land- 

 vertebrates ; or they may be employed during leaping from heights, so 

 as to produce oblique instead of vertical descent. The latter is the use 

 exemplified in land-vertebrates, and is necessarily associated with the 

 power of climbing, by means of which the animal may attain the height 

 required, and therefore with the possession of climbing organs. True 



* Jahresber. Scliles. Ges., Ixxvii. (1900) pp. 2-15. 

 T Proc. Nat. Sci. Philadelphia, 1900, pp. 568-S1. 

 % Zool. Jahrb. (Abt. Syst.), xiv. (1900) pp. 49-G1. 



