ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 657 



of vital processes. It concludes with an exposition of the author's 

 doctrine of Entelechy as a factor in Nature. 



Wild Fauna of Kew.* — W. T. Thiselton-Dyer has edited an 

 interesting volume on the wild fauna and flora of the Royal Botanic 

 Gardens at Kew. It is very instructive to look over the census — con- 

 fessedly incomplete — of the forms of life which occur, or have occurred, 

 in this small area. They range from foxes to animalculse, and some 

 of them are surprising : 17 mammals, 28 songsters and many other 

 birds, 2 reptiles, 5 amphibians, 10 fishes, 44 Gastropods, 4 bivalves, 

 59 Entomostraca, 6 Isopods, 10 centipedes, 13 millipedes, 39 Orthoptera, 

 150 Lepidoptera, many other insects, 134 spiders, 12 harvestmen, 

 12 water-mites, 21 exotic earthworms, 2 leeches, 120 Rotifers, 3 sponges, 

 and 2 Protozoa. Numerous authorities have co-operated in furnishing 

 the lists. 



Adaptive Modifications of Limb Skeleton.! — R. C. Osburn reviews 

 and discusses the various modifications in the limbs of aquatic reptiles 

 and mammals. The groups considered especially are the Cetacea, 

 Sirenia, Ichthyosauria, Plesiosauria, Mosasauria, Thalattosuchia, and the 

 less modified Pinnipedia and Ghelonia. The modifications which appear 

 to be the most usual and of greatest importance in the change from the 

 terrestrial to the natatory type of limb are : 



1. Abbreviation of the limb as a whole. This is seen especially in 

 forms with tail fin well developed, as the Cetacea and Sirenia, in which 

 the hind limb is lost entirely, and in Ichthyosauria, some of which have 

 the hind limb very much reduced. The shortening always begins in the 

 proximal end of the limb. 



2. Curvature or backward extension of the limb^ attained in various 

 ways — e.g. curvature of bones of limb or of digits, suppression of carpus 

 and tarsus towards the posterior side. 



3. Distal dilatation or broadening, so as to form paddles. The most 

 common method is found in the spreading of the digits, as in all aquatic 

 mammals, and in aquatic reptiles generally, except the Plesiosaurs 

 and the Ichthyosaurs, where spreading of the digits is rare and slight. 

 Also the breadth of the bones of the digits may be increased sufficiently 

 to make this portion of the limb the widest — e.g. in Sirenia, Plesiosaurs, 

 and some Ichthyosaurs. 



4. Parallelism of fore and hind limbs. The Pinnipedia are an 

 exception. 



5. Tendency toward the loss of the hind limb. This is found almost 

 without exception in those forms w T hich have developed a caudal fin. In 

 such forms the tail becomes a much more efficient propelling organ than 

 the limbs, and the latter are of use chiefly as organs of equilibration. 

 The anterior limbs, from their position, are naturally more useful in 

 this respect than the posterior, and the latter tend toward reduction. 



6. Tendency toward similarity in shape and function of all the bones 

 of the limb — a degenerative process. 



* Kew Bulletin, additional series 5, London, 1906, 223 pp. 

 t Annals New York Acad. Sci., xvi. (1906) pp. 447-82 (3 pis.). 



