PROGRESS OF MICROSCOPICAL SCIENCE. 
315 
fact, such an occurrence has been actually seen to occur, so that it 
would seem that the whole matter is capable of a reasonable and 
simple explanation, and we may es;pect to hear of similar downfalls 
in other localities." 
The Structure of the Cells of the Spinal Ganglia. — This, which has 
many times been investigated, has lately been taken up by Herr E. 
Arndt, who, in a paper published in Max Schultze's ' Archiv ' (vol. xi.), 
states that the typical form of the cells of the spinal ganglia is a more 
or less irregular flat disk. They are at least bipolar. The author 
believes that multipolar cells also exist, which, in addition to two 
strong and well-marked processes, send out a number of finer ones, 
which are, however, easily torn off or overlooked. Herr Arndt was 
unable to convince himself of the existence of unipolar ganglionic 
cells. The apolar bodies which do occur in the spinal ganglia, the 
author regards as the result of an anomalous development. The two 
chief processes of the ganglionic cells generally arise very near each 
other. In many cases each process arises from the ganglionic cell by 
itself, and is enclosed in a special sheath, which is a continuation of 
the capsule. In other cases the two processes approach each other, 
and are enclosed in the same sheath. They are medullated almost at 
their origin, but the author has observed processes originally non- 
medullated. 
The Vocal Organs of the Cicada. — The ' Academy ' has recently 
published among its interesting microscopical notes an account of a 
French investigation of the above-named organs. It says that M. 
Carlet, who has been inquiring into the subject, finds that the 
researches of Eeaumur, Carus, Duges, and others, are somewhat 
inaccurate. M. Carlet (in the ' Comptes Eendus ') states that the 
singing cicada has three pairs of thoracic stigmata, the two first 
situated immediately below the spiny plates of the mesothorax, while 
the two last belong to the metathorax, and are covered by the spiny 
plates of this thoracic segment, which are the lids of the musical 
apparatus of the male. These three pairs of thoracic stigmata " he 
is certain exist also in the females." The two last thoracic stigmata, 
he states, were mistaken by Carus for the two first of the abdomen, 
from which they differ in position and structure. The thoracic 
stigmata are very large, hairy at the margin, surrounded by a horny 
circle, and furnished with movable lids, while the abdominal ones 
are small, punctiform, destitute of movable lids, and surrounded by 
a little mealy aureole. There are seven pairs of abdominal stigmata, 
not six, and the first are situated on the scaly triangle of the first 
abdominal ring. The second pair have no mealy circle, and are less 
visible than the others. The external wall of the sonorous cavity in 
which the drum is situated does not, according to M. Carlet, belong to 
the first abdominal ring as Eeaumur figured it, but to the second, as 
is readily seen in C. orni and C. maculati, in which the wall is 
incomplete, and forms a salient apophyse projecting on the second 
segment. In C. pleheia it is easy to see that the superior margin of 
this external wall is free, and separated from the upper margin of the 
