SCIENTIFIC SUMMAEY. 399 
useful class of instrument, I lay claim to no credit connected with, it, much 
less to hemg its inventor.” 
The Problem of Maliomefs Coffin. — M. Plateau undertook last year a series 
of experiments, with a view to discover whether, hy any combination of 
magnets, he could suspend a metallic body in mid-air, as Mahomet’s coffin is 
supposed to be maintamed ; and the result was his conclusion that the con- 
dition is an impossible one. This led to considerable discussion upon 
the question ; and a letter appeared from Mr. W. F. Bartlett, of the Eoyal 
Institute, m the pages of the Reader, fully confirming M. Plateau’s view. In 
this, however, he described a beautiful experiment, wdiich may be new to our 
readers. A piece of gold leaf, about two and a half inches long and an inch 
and a quarter wide, was cut into the form of a kite, one end forming an 
obtuse and the other an acute .angle. A large Leyden jar, with an elevated 
knob, having been charged, the gold leaf, lying on a piece of paper, was pre- 
sented to it. It was sometimes necessary to detach the leaf by the aid of 
a penknife ; when detached, it sprang tov/ards the knob, but stopped within 
two inches of it, and remained hovering in the air. Its tail waved like the 
tail of a fish ; and when a point projected from its side, it rotated continually. 
The jar when carried through the room was followed by the fish, which con- 
tinued to swim in the presence of the knob for nearly an hour. With smaller 
jars and smaller fragments of gold, the same experiments may be made. — 
Vide the Reader, February 11th. 
ZOOLOGY AND COMPAEATIVE ANATOMY. 
The Mammary Gland of the Echidna hystrix. — The Echulna hystrix, or 
porcupine ant eater, is one of those curious monotremes found only in Aus- 
tralia and Van Diemen’s Land. For many years the history of its extra- 
uterine development has been a sealed book to zoologists ; but the beautiful 
and elaborate memoir which Professor Owen has just presented to the Eoyal 
Society, upon the anatomy of the mammary gland of this creature, has 
entirely cleared up our notions concerning the lactation of the lower mono- 
tremata. Like the milk-gland of other mammals, the secreting organ of the 
Echidna is of a lobular character, that is to say, it is composed of a number 
of caeca bound together with connective tissue, and supplied abundantly 
with blood-vessels. Whilst, however, in other mammals, the general cavity 
into which the lobules open is connected with a teat, through which the 
young animal receives the milk, in the Echidna this receptacle absolutely 
receives the head of the young creatures. Professor Owen has demonstrated 
this fact incontrovertibly. Thus the Marsupalia carry their young in a pouch, 
which is a veritable cradle, in which they are nursed, but the Monotremes 
simply present a cavity into which the nurseling can only place its head, and 
so receive the nutritious secretion from its mother. The Professor has found 
that the claws of the anterior limbs are quite disproportionately developed in 
the young Echidnae, attaining a considerable size ; this he believes is to enable 
them to attach themselves to the mammary pouch, and thus prevent the 
strain that otherwise would fall upon the neck. As far as an examination of 
the uterus went, there was no trace of placenta exhibited ; and hence Pro- 
