SCIENTIFIC SUMMARY. 
221 
Bor could lie discover any direct means of communication between the 
vascular system and the sea-water, any aperture, however minute, through 
which nutritive material might have been introduced into the system of the 
animal, and after careful investigation he was forced to the conclusion, that 
these anomalous little creatures were nourished by the direct absorption 
through the ectoderm of organic material dissolved in sea-water. This is 
however, not altogether an isolated case, as M. Mereschkowsky has demon- 
strated that in certain sponges nourishment is effected in a similar fashion. 
As several of these little Medusae occur about our own coasts, it would be an 
interesting point to ascertain whether any of them present analogous pheno- 
mena, and if possible to ascertain why a structure necessitating so abnormal 
a method of nutrition occurs. 
Migrations of Aphides. — M. Lichtenstein has announced his discovery of 
some very curious facts in the life-history of certain aphides ( Comptesrendus , 
November 18, 1878). He first detected migrations of Phylloxera quercus 
from Quercus cocdfera to Quercus pubescens ; and these observations were con- 
firmed by those of M. Targioni Tozzetti upon Phylloxera Jlorentina, which 
passes different stages of its life upon Quercus ilex and Quercus peduncu- 
lata. 
M. Lichtenstein has since found that the aphis of the galls of the Pis- 
tachio (Anopleura lentisci) passes from those galls to the roots of at least two 
species of grasses {Bromus sterilis and Hordeum vulyare). He describes the 
development of the aphis somewhat as follows : — 
In May and June the egg deposited on the pistachio by the fertilised 
female produces an apterous insect, the Founder (first larval form) which pro- 
duces the gall, and after four moults gives birth asexually to young aphides 
destined to acquire wings and, after four moults, to produce the Emigrants 
(second larval form) which quit the gall, fly to the grasses, and there produce 
asexually apterous young, the Budders (third larval form), which breed asexu- 
ally underground, producing several apterous generations until the appear- 
ance of nymphs which furnish the Pupifera (fourth larval form) which issue 
from the ground and fly to the Pistachio, where they deposit their pupae which 
produce sexual individuals, the females of which deposit the true eggs con- 
stituting the starting point of the whole series. If this complicated de- 
velopment be correctly described, it is of much interest, as it may apply to 
many other species of aphides, and in that case would throw important light 
upon many points in their history. 
The Gymnotus. — From an examination of a fresh specimen of Gymnotus 
electricus M. Fritsch concludes that this fish is allied to the siluroids 
rather than to the eels. He founds this opinion especially upon the 
structure of the brain, which has the olfactory tubercles small and the 
cerebellum very large, as in the Siluroidei ; whereas in the true eels these 
parts present exactly the opposite character. Further, in the Gymnotus , as 
in the siluroids, the maxillaries are rudimentary, and the margin of the 
upper jaw is formed by the intermaxillaries ; in the Mursenoids, on the 
contrary, the maxillaries form parts of this margin and bear teeth. The 
structure of the opercula constitutes another agreement with the Siluroids. 
From a consideration of these and other characters M. Fritsch is inclined 
to place the Gymnotini close to the Malapterurini, which also include an 
