448 General Notes. 3 [ June, 
The asymmetry of the brain is remarkable ; the large ganglionic 
cells are most abundant in the center behind the middle and from 
there to the posterior side of the brain; a median line is slightly 
indicated by the arrangement of the fungoid masses. The tract 
composed of large nerve fibres with scattered ganglionic cells on 
the Jeft side is very much more extensive than on the right. 
Comparison with the brain of other Arthropods.—So wholly 
unlike in its form, the want of antennal nerves, and internal struc- 
ture, is the supra-cesophageal ganglion, or “ brain,” of Limulus 
to that of insects and the higher Crustacea, that it is very difficult 
to find any points of comparison. 
Histologically, judging by my specimens of the brain of the 
lobster which are stained with carmine, the brain of Limulus 
agrees with that of other Arthropods in having similar large 
ganglion-cells; the smaller ganglion-cells, so abundant in the 
brains of insects and Crustacea, are wanting in Limulus. There 
are, in Limulus, no da//en-substanz-masses homologous with those 
of the other Arthropods nor any “mush-room”’ bodies. 
Topographically the internal structure of the brain of Limulus 
is constructed on a wholly different type from that of any other 
Arthropodous type known, so much so that it seems useless to 
attempt to homologize the different regions in the two types of 
brain. The plan is simple in Limulus; much more complex in 
Arthropods, especially in the brain of the craw-fish, as worked 
out by Krieger, as in the Decapodous brain there arise two pairs 
of antennal nerves besides the optic pair, and in external form the 
two types of brain are entirely unlike. The symmetry of the 
brain of the crayfish, as of the lobster and insects, is marked 
throughout, each hemisphere exactly repeating in its internal 
topography, the structure of the opposite side; the symmetry of 
that of Limulus is obscure and imperfect. 
Tue Foop or Brrps.—Under this title Prof. S. A. Forbes has 
. published in the Transactions of the Illinois State Horticultural 
Society, a valuable report on the food of the thrushes. In Ilinois 
there are estimated to be three birds to an acre during the six 
summer months. We make the following extracts: “It is my own 
opinion that at least two-thirds of the food of birds consists of 
insects, and that this insect food will average, at the lowest rea- 
sonable estimate, twenty insects or insects’ eggs per day for each 
individual of these two-thirds, giving a total for the year, 7200 
r acre, or 250,000,000,000 for the State—a number which, 
placed one to each square inch of surface, would cover an area of 
40,000 acres. 
“Careful estimates of the average number of insects per square 
yard in this State, give us at farthest 10,000 per acre for our whole 
area. On this basis, if the operations of the birds were to be 
suspended, the rate of increase of these insect hosts would be 
accelerated about seventy per cent., and their numbers, instead of 
