The Penycuik Experiments : l An Appreciation. 



By J. Arthue Thomson, M.A. 



Without raising the vexed question of the relative value of reflection 

 and experiment, or admitting that the antithesis is a just one, we may 

 take it that one of the most hopeful signs of progress in evolution- 

 theory is the increasing prominence of experimental work, and it is on 

 this general ground first of all that we welcome Prof. Cossar Ewart's 

 studies in heredity, well known in interested circles as " The Peny- 

 cuik Experiments." For it is certain that we have here no fireside 

 musings as to what might be, but the work of a persistent and patient 

 experimenter, with his coat off and his sleeves up, trying to discover 

 what is. 



In giving some account of what has been done by Prof. Ewart, 

 one meets the difficulty that most of the points tested are necessarily 

 concerned with individual animals, which, however familiar to the 

 experimenter, are very apt to get mixed in the mind of an outsider. 

 In order, then, to avoid the somewhat fatiguing exercise of keeping 

 Matopo and Mulatto, Romulus and Remus, Biddy and Brenda, Norette 

 and Hekla, as clear individualities in the mind — which is easy enough 

 with the beautifully illustrated book before us — we propose to find the 

 thread of our summary rather in the general ideas than in the 

 fascinating living things. And the ideas round which the experi- 

 ments have arisen are Reversion, Prepotency, Inbreeding, Telegony. 



Reversion. 



A great part of the work done concerns zebra hybrids, of which 

 nine (zebrules) were got from the Burchell zebra stallion, Matopo, and 

 various mares, and others from zebra mares served by pony (zebrinnies) 

 and donkey. These hybrids, charming and beautiful creatures, may 

 turn out to be of high practical value, but their present interest is 

 mainly theoretical. 



It may be pointed out first of all that the numerous previous 



1 "The Penycuik Experiments," by J. C. Ewart, M.D., F.R.S., Regius Professor of 

 Natural History, University of Edinburgh. 8vo. pp. xciii. + ]77, with 46 figs. London : 

 A. and C. Black, 1899. 



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