180 



of Datura! $|ttarg; 



says, " Professor Kaup and Dr. Klipstein have 

 recently published a description and figures 

 of this' head, in which they state that the 

 very remarkable form and dispositions of 

 the hinder part of the skull show it to have 

 been connected with muscles of extraordi- 

 nary power, to give that kind of movement 

 to the head which would admit of the 

 peculiar action of the tusks in digging into 

 and tearing up the earth. They further 

 observe that my conjectures respecting the 

 aquatic habits of this animal are confirmed by 

 approximations in the form of the occipital 

 bone to the occiput of Cctacea ; the Dinothe- 

 rium, in this structure, affording a new and 

 important link between the Cetacea and 

 the Pachydermata." 



DIODON. A remark able genus of Plectog- 

 nathi, or bony fishes with soldered jaws. 



The DIODON HYSTRIX, commonly 

 termed the Sea-Porcupine, is of a nearly 

 spherical form, sometimes measuring not 

 less than two feet in length ; but it possesses 

 the power of inflating or contracting itselt at 

 pleasure by means of an internal skin or 

 membrane situated beneath the exterior or 

 spiny covering. Its colour is a pale grey, 

 the back being of a somewhat deeper cast ; 

 and the whole body is marked at the base 

 of each spine by a round black spot ; the 

 fins being also spotted. When taken by a 

 line and hook, it inflates its body and 

 elevates its spines to the highest possible 

 degree, as if endeavouring to wound in all 

 directions ; nor can it be touched without 

 danger until it is dead. It is a native of the 

 Indian and American seas ; and its flesh is 

 coarse and worthless. 



The OBLONG DIODON (Diodon atinga) 

 differs from the former in being of a more 

 lengthened shape, and in having the spines 

 rather round than triangular. Its general 

 colour IB grey, deeper on the back, and with 

 a cast of pink on the lower parts like the 

 Diodon Hystrix : it is marked with numerous 

 round black spots ; but it is only from twelve 

 to fifteen inches in length. Unless very 

 carefully cleaned, it is dangerous to eat it ; 

 for if not absolutely poisonous, the flesh is 

 highly unwholesome. It ia a native of the 

 Indian and American seas. 



Besides the above, there is the ROUND 

 DIODON (Diodon arbicularis), about nine or 

 ten inches in length ; which is considered a 

 poisonous fish: PLUMIEU'S DIODON (Dio- 

 don Plumieri), a species very nearly allied to 

 the Oblong Diodon : and the PATCHED DIO- 

 DON (Diodon liturosus), which inclines to a 

 globular shape, and is marked on each side 

 of the body with an oval patch and two 

 transverse ones ; and on the back a round 

 spot encircling the dorsal fin : spines white 

 with brown tips, and all the fins greenish 

 yellow. 



" One day," says Mr. Darwin (while on 

 the coast of Brazil), " I was amused by 

 watching the habits of a Diodon, which was 

 caught swimming near the shore. This fish 

 is well known to possess the singular power 

 of distending itself into a nearly spherical 

 form. After having been taken out of water 



for a short time, and then again immersed 

 in it, a considerable quantity both of water 

 and air was absorbed by the mouth, and 

 perhaps likewise by the branchial apertures. 

 The process is effected by two methods ; the 

 air is swallowed, and is then forced into the 

 cavity of the body, its return being pre- 

 vented by a muscular contraction which is 

 externally visible ; but the water, I ob- 

 served, entered in a stream through the 

 mouth, which was wide open and motionless ; 

 this latter action must therefore depend on 

 suction. The skin about the abdomen is i 

 much looser than that of the back ; hence, ' 

 during the inflation, the lower surface be- i 

 comes far more distended than the upper ; 

 and the fish, in consequence, floats witli its 

 back downwards. Cuvier doubts whether 

 the Diodon, in this position, is able to swim ; 

 but not only can it thus move forward in a 

 straight line, but likewise it can turn round 

 to either side. This latter movement is 

 effected solely by the aid of the pectoral 

 fins, the tail being collapsed, and not used. 

 From the body being buoyed up with so 

 much air, the branchial openings were out 

 of water : but a stream drawn in by the 

 mouth constantly flowed through them. 



" The fish, having remained in this dis- 

 tended state for a short time, generally ex- 

 pelled the air and water with considerable 

 force from the branchial apertures and 

 mouth. It could emit, at will, a portion of 

 the water; and it appears, therefore, pro- 

 bable, that this fluid is taken in partly for 

 the sake of regulating its specific gravity. 

 This Diodon possessed several means of de- 

 fence. It could give a severe bite, and could 

 eject water from its mouth to some distance, 

 at the same time it made a curious noise by 

 the movement of its jaws. By the inflation 

 of its body, the papillae, with which the skin 

 is covered, became erect and pointed. But 

 the most curious circumstance was, -that it j 

 emitted from the skin of its belly, when 

 handled, a most beautiful carmine red and 

 fibrous secretion, which stained ivory and 

 paper in so curious a manner, that the tint 

 is retained with all its brightness to the 

 present day. 



DIOMEDEA. A genus of Palmiped birds. ' 

 [See ALBATROSS.] 



DIOPSIS, or TELESCOPE TLY. A 

 very singular genus of Dipterous insects, re- 

 markable for the enormously developed pe- 

 dicels on whir.h the eyes are situated. They 



