2 DOUBLE MONSTROSITY— OCCURRENCE, RECORDS, ETC. 



13 not far from corresponding with its frequency in those of the fowl. Dareste's (53) figures showed 

 out of 10,000 eggs, 38 examples of double and 2 of triple monstrosity, an average of 1 in 250. 



Eecords of double monster fish do not seem to have come down to us from the ancients, 

 and although the Fish has been employed in symbolism and mythology since earliest times, no 

 shape it has received seems to indicate such acquaintance with its teratology as is undoubtedly 

 implied for that of the higher animals in the Janus, Cerberus, Cyclops, and other fables. The reason 

 is not far to seek. With the rarest possible exceptions, monster fish die off so soon as the store 

 of food contained in the eggs on which they develop has been exhausted, and at this period they 

 are still small in size and remote from ordinary observation. 



The first notice of a double monster fish appears to be that contained in the Monstrorum 

 Historia of Aldrovandi (2), a work brought out some thirty years after Aldrovandi's death by his 

 loyal pupil Ambrosini. The notice bears out that a two-headed fish almost as large as a crocodile 

 was caught in the Nile near the town of Latislana. The figure appended is that of a monster 

 shark-like fish. No shark-like fish, however, seems to be the inhabitant of the Nile (Boulenger, 

 Brit. Mus. Cat. " Fresh- water Fishes of Africa," i. 1909). Examples of double-headed shark or 

 dog-fish embryos are not unknown (see under Selachoidei, above, and on p. 31), and in all proba- 

 bility some such specimen supplied the substratum of the record and story. 



The only instances of survival or reputed survival of fish exhibiting a major type of monstrosity 

 which I have been able to come across are the following: (1) The story in Aldrovandi given 

 above; (2) Perfectly authentic accounts by Secques (224) of a gasteropagous twin Salmo lacustris 

 and of another similar twin Salmo fario. Both examples were about fifteen months old. In the 

 first, one of the twins was larger than the other and measured about 6 J inches. In the second, 

 the twins were of equal size, each being rather more than 5 inches in length. (3) A notice in 

 Yarrel (275, ii. p. 107) from a Cambrian newspaper of 28th November, 1829, regarding the capture 

 of a " fine Salmon with two heads and two tails. The heads are joined on one neck and the tails 

 meet about the centre. The fish is now to be seen alive in a small pool at Llangattock." (5) 

 Account of a cyclopic ray by Paolucci (181), referred to further on p. 43. F. Buckland (33a) also 

 mentions that he " once read an account of a double-headed catfish (Anarrichas lupus) having been 

 caught in the North Sea." 



Jacobi (10S) seems to have been the first not only to make systematic observations on the 

 artificial breeding of trout, but also to note and describe the monstrosities which made their 

 appearance in the broods, and to speculate on the causes of their occurrence. A translation of his 

 highly interesting original letter on the subject will be found in Yarrell (275, ii. 87-96). As 

 teratology developed into an exact science in the hands of Meckel (156), St. Hilaire (213), 

 v. Baer (5), Yrolik (266), and others, careful attention was paid to the study of monstrosities in 

 fishes, particularly since their growth and development could be observed in the living condition 

 with the aid of the microscope. It is probably to St. Hilaire's influence that we owe the studies of 

 Valentin (263), Quatrefages (197-8), Coste (4-3), and Lereboullet (14-1-3), which followed each 

 other closely towards the middle of last century. Lereboullet's work is particularly valuable, and 

 still remains as containing standard results. Some of these have been already noted, while others 

 are referred to under Causation (p. 5) and Structure (p. 10). 



Later, the careful studies in normal embryology, of which His's observations on the develop- 

 ment of the bony and cartilaginous fishes are an example, had their influence in stimulating renewed 

 observations by means of the newer methods on the origin and structure of monstrosities in fishes 

 (Oellacher 176, Bauber 200-2). Very useful work along descriptive, classificatory, and historical lines 

 has also been done by Knoch (127), Panum (180), Bauber (200-2), Klaussner (123), and more 

 lately by "Windle (272) and Schmitt (216). The methods of experimental embryology, particularly 

 in the hands of Kopsch (129-133) and Morgan (161-2), have supplied evidence of the greatest 

 value in regard to the processes of normal and teratological development. On the structural 

 side, our knowledge of detail has gradually been elaborated by the work of Bauber (202), Oellacher 

 (176), Schmitt (216), Moser (165), Barbieri (6-7), and the author (76-77). 



