GLOBE-FISHES. 
429 
Globe-Fishes. 
continuous. The elongate tail terminates in a forked fin; and the body is invested 
with spiny bony plates, which do not overlap one another. The single species, which 
may attain a length of 20 inches, ranges over the Indian and Malayan seas, and is of 
a general brown colour, with a spot of variable colour on the sac, and the fins yellow. 
The essential characteristics of the globe-fishes, which form the 
second subfamily, are that the tail and its fin are distinct and well 
developed, and that a portion of the oesophagus is highly distensible and capable of 
being inflated with air. All the globe-fishes, or, as they are sometimes called, sea- 
hedgehogs, are easily recognised by the short and cylindrical or rounded form of 
the body; which is generally covered with a scaleless skin bearing a number of 
spines of variable size. When these spines are of large size, they are spread uniformly 
over the whole body, but when small they are partial in their distribution. These 
fishes are divided into two groups, according to the nature of the dental plates. In 
the first, or small-spined group, as typified by the genus Tetrodon ,—of which a 
species is represented in the lower figure of the coloured Plate,—the dental plate of 
each jaw is divided by a median suture, and the spines are frequently very small, 
and may be even altogether absent; many of the species being very brilliantly 
coloured. One member of the genus inhabits the rivers of Brazil, and a second 
those of West Africa and the Nile, while a small form is found in the brackish- 
water estuaries of India. According to Bay, the flesh of some of the species is 
poisonous, while that of other kinds is eaten by the Andamanese and Burmese. 
In the second group, of which the porcupine globe-fish (Diodon hystrix ) is shown 
in the lower figure of the coloured illustration, the dental plates in the jaws are 
undivided, and the spines are large and frequently erectile. In addition to the 
undivided dental plates on the edge of the jaws, in the members of this group 
there is another crushing plate in the middle of the palate, opposed by a similar 
one in a corresponding position in the lower jaw; these plates being divided by a 
median suture, and from their laminated structure forming most admirable 
triturating instruments. The porcupine globe-fish, which may measure fully a 
couple of feet in length, is distributed over both the Atlantic and Indo-Pacific 
Oceans, where it is accompanied by the smaller spotted globe-fish (D. maculatus). 
Fossil diodons have been discovered in the Miocene strata of Malta and Sicily, as 
well as in the middle Eocene of Monte Bolca, and in other Eocene beds on the 
coasts of Algeria and Arakan; while an extinct genus has also been recorded from 
the Italian Eocene. In their normal state the globe-fishes have rather elongated 
cylindrical bodies, but they are able to assume a globular form by swallowing air, 
which passes into the oesophagus and blows out the whole animal like a balloon, 
with the spines standing out at right angles from the tense skin. In this condition 
the fish naturally floats back-down wards, and it is then driven to and fro on the 
ocean-surface by waves and currents in a perfectly helpless condition; although 
the bristling spines render it perfectly safe from all attack. Hie distention is, 
therefore, evidently for the purpose of defence; and it has been suggested that 
when swimming below the surface these fishes may inflate themselves in a similar 
manner by swallowing water instead of air. When desirous of returning to its 
normal condition, the fish expels the air from the oesophagus through the mouth 
and gill-openings; a loud, hissing noise being produced by the expulsion. 
