394 THE ZOOLOGIST. 



BRITISH ASSOCIATION FOR THE ADVANCEMENT OF 

 SCIENCE, BIRMINGHAM, 1913. 



ADDRESS TO THE ZOOLOGICAL SECTION. 



By H. F. Gadow, M.A., Ph.D., F.R.S., President of the Section. 

 (Concluded from p. 360.) 



Categories of Homoplasy. 



Isotely. — If the character, feature, or organ has been evolved out 

 of homologous parts or material, as is most likely the case in closely 

 related groups, and if the subsequent modifications proceed by 

 close resemblance. Iso-tely : the same mark has been hit. 



Homceotely. — Although the feature has been evolved from homo- 

 logous parts or material, the subsequent modifications may proceed by 

 similar stages and means, there is a fair probability or chance of very 

 different stages and means, and the ultimate resemblance will be 

 less close, and deficient in detail. Such cases are most likely to 

 happen between groups of less close affinity, whether separated by 

 distance or by time. Homceo-tely : the same end has been fairly well 

 attained. The target has been hit, but not the mark. 



Parately. — The feature has been evolved from parts and material 

 so different that there is scarcely any or no relationship. The 

 resulting resemblance will at best be more or less superficial ; some- 

 times a sham, although appealing to our fancy. Para-tely : the 

 neighbouring target has been hit. 



Examples. 

 Isotely ; Bill of the Ardeidce Balaniceps (Africa) and Cancroma 

 (Tropical America). 

 Zygodactyle foot of Cuckoos, Parrots, Woodpeckers (^). 

 Patterns and coloration of Elaps and other snakes. 

 Parachute of Pctauriis (marsupial) ; Pteromys (rodent) and Galeo- 



pithccus. 

 Perissodactylism of Litoptema and Hippoids. 

 Bulla auris of Plioplatecarpus (Pythonomorphe) and certain 



Whales ; if tympanic = quadrate. 

 Grasping instruments or nippers in Arthropods : pedipalps of 



Phryne ; chela? of Squill; first pair of Mantis' legs. 

 General appearance of Moles and Notoryctes, if both considered as 

 mammals ; of Gulls and Petrels, if considered as birds. 

 Ilomceotcly : Heterodactyle foot of Trogons ( 2 -}j . 

 Jumping foot of Macropus, Dipus, Tarsius. 

 Intertarsal and cruro-tarsal joint. 



Fusion and elongation of the three middle metarsals of Dipus and 

 Rhea. 



Paddles of Ichthyosaurs. Turtles, Whales, Penguins. 



