SCIENTIFIC SUMMARY. 
333 
ing the mode in which certain fishes of the rivers in that region, especially 
Siluroids and Characini, are enabled to emit sounds. The organ implicated 
in this phenomenon is, according to him, the air-bladder, which is peculiarly 
modified. In the Siluroids, the unossified part of the air-bladder is elastic 
throughout, whilst in the Characini the elasticity chiefly depends upon flat 
bands or round cords situated in the wall. In the Siluroid genera Platy stoma 
and Pseudaroides, the air-bladder is divided by a longitudinal partition and 
by several transverse ones into a number of chambers which, however, still 
communicate with each other. In Doras , it has numerous appendages divided 
by imperfect septa into a great many small cells. In all these fishes the 
transverse processes of the two or three first vertebrae, and often a part of 
the arch of the first vertebra, are bound together and to the hinder part of 
the skull by strong elastic membranes. The transverse processes of the first 
or second vertebrae, and sometimes of both, are formed into powerful springs 
and closely bound to the air-bladder. The sound is produced by the action 
of muscles inserted, either directly upon the air-bladder, or upon the trans- 
verse process of the third vertebra. In the Characini, the elastic parts of the 
air-bladder are stretched lengthwise by the contraction of the muscles, and 
the vibration produced by this movement is transmitted to the air contained 
in the cavity of the bladder. In the Siluroids the forepart of the air-bladder 
is drawn alternately forward and backward by the contraction and relaxa- 
tion of the muscles, and the air passing by the imperfect transverse par- 
titions sets these in motion and causes the sounds. — ( Comptes rendus , 
May 19, 1879.) 
Trichina in the Hippopotamus. — M. E. Heckel announces the occurrence 
of Trichina in great abundance in a young hippopotamus received from 
Egypt, which lived for about four months in the Zoological Gardens at Mar- 
seilles. The animal suffered from skin disease, taking the form of great 
suppurating boils, during the whole of its residence at Marseilles. On ex- 
amination these sores were found to have penetrated the skin, and to lead to 
great cysts filled with pus in the subcutaneous tissue. It was after the 
greater part of the flesh had been thrown away that M. Heckel detected the 
Trichina in the muscles surrounding one of the cysts which he had kept, 
and he was unable to ascertain whether the trichinosis and the external 
symptoms were in any way correlated. The discovery of the parasite in 
this great Pachyderm is of interest. — ( Comptes rendus, June 2, 1879.) 
Metamorphoses of the Blister-Beetles. — The transformations of the common 
blister-beetle, or so-called Spanish fly of the shops ( Lytta vesicatoria ) have 
eluded the researches of entomologists, although the insect itself is exceed- 
ingly abundant on ashes and other trees in the south of Europe. The 
life-history of other species of the same family ( Mdoie , Sitaris, Epicauta ) has, 
however, been worked out, and entomologists will be glad to leam that M. 
Lichtenstein, guided by the results obtained in the investigation of those 
forms, has at last succeeded in solving the problem and demonstrating that 
the stages through which the officinal blister-beetle passes are very similar 
to those presented by its nearest relatives. 
At the end of May, or the beginning of June, the females deposit their 
eggs in small excavations in the ground ; the eggs are elongated, whitish, 
and transparent, and each female lays several hundred of them in a small 
