248 The Irish Nat7iralist. December, 191 2. 



REVIEW. 



MONSTER FISHES. 



The Teratology of Fishes. By James F. Gemmill, M.A., M.D., D.Sc. 



pp. xviii and 74. 4to. Plates i. — xxvi. Glasgow ; James 

 Maclehose and Son, 1912. Price 155. net. 



Teratology " may be defined as the stndy of the abnormal duplication 

 of organs. In the higher mammals, it has supplied us with the fables of 

 Cerberus and Cyclops. The phenomenon is by no means so rare as one 

 would expect, and it escapes observation ovv'ing to the fact that the great 

 majority of individuals exhibiting monstrous growths die at a very early 

 stage in development. Figures showing the relative frequency of monsters, 

 as estimated by various observers, vary within very wide limits. Whilst 

 investigating abnormal development in the Salmonidae, Gemmill found 

 that the proportion showing double monstrosity was i in 200-350. 



In the present work the author deals chiefly with abnormal duplications 

 of considerable magnitude, especially those occurring in the Trout and 

 the Salmon. These fishes offer peculiarly favourable conditions, owing 

 to the ease with which development can be followed, and the abundance 

 of material available in hatcheries. The chief major abnormalities are 

 (i) doubling at the anterior end ; (2) doubling at the posterior end ; 

 (3) doubling at both ends, and (4) doubling only in the mid -region of the 

 body. In addition to giving a detailed account of his own researches, 

 the author briefly summarises the results and opinions of other workers. 



Satisfactory explanations of the origin and causation of abnormal 

 duplication are not yet forthcoming, but the author briefly states the 

 conclusions to which his studies have led him. He is of the opinion that 

 monsters may be produced either by spontaneous germinal variation, or 

 by the direct action of the environment during development. In the 

 former case the characters are innate, in the latter case they are acquired. 

 If the monsters survive and reproduce, those originating from a germinal 

 variation transmit their malformations to their offspring, whilst there 

 is no evidence that those originating by the action of the environment 

 do so. The malformations, whether of innate or acquired origin, tend to 

 develop along certain lines of instability. The author does not tell us how 

 we are to distinguish between the results arising from innate and acquired 

 variation, and till that can be done it seems useless to say that the one is 

 transmissable, and the other is not. 



The, volume is furnished with an extensive Bibliography of the subject, 

 and illustrated with twenty-six plates of photomicrographs of specimens 

 and sections which are, unfortunately in many cases too small to show 

 the necessary detail. 



The study of Teratology throws many interesting sidelights on the norm.al 

 processes of development, and this book certainly justifies Dr. Gemmill's 

 claim that the subject merits an important place in the biological field. 



R. S. 



