SOME POINTS IN THE ANATOMY OF THE PLATYDESMIDA. 515 
being much compressed, and extending as far forwards and 
downwards as laterally. The frontal lobes are short and 
thick, and at the end of each a short thick nerve is given off 
which runs to the sense organ described at the beginning of 
this paper. ‘his is evidently one of the class of organs 
which St. Remy calls the organs of Tomésvary. The frontal 
lobes are united by a thick mass of nervous tissue, the pont 
pneumogastrique of St. Remy, from which the pneumogastric 
nerve is given off. Below the frontal lobes are the antennal 
lobes, which are not so well developed as in most of the 
brains described before, and it is not until they are examined 
by means of sections that they can be made out clearly, 
except for the antennal nerve which is given oft from each 
and passes to the antenna. Just at the junction of the 
antennal lobes with the frontal, the cesophageal commissures 
pass off embracing the cesophagus and passing downwards 
to the ventral ganglionic cord. Below the cesophagus they 
are united by a slender transverse commissure, which, as seen 
in fig. 7, is small in comparison with the mass of the brain, 
and the space between the commissure and the ventral 
ganglion 1s very narrow in comparison with that in other 
brains. 
The nerve from the sense organ before mentioned passes 
off from the frontal lobe just before the plane where the 
cesophageal commissure is given off, and is shown in fig. 5, 
amass of ganglion cells is situated at the point where the 
frontal lobe is continuous with the nerve, the nerve itself is 
short and fibrous, the fibres continuing into the hypodermis. 
The pigment which covers the hypodermic cells lining the 
transparent chitinous exoskeleton of the head and gives it 
its colour is darkened at the edges of the clear chitin of the 
organ, so as to form a sort of diaphragm, and below the clear 
thickening of the organ, the hypodermic cells are modified, 
and form a thick mass, with which the fibres of the nerve 
are continuous. When the hypodermis is depigmented with 
nitric acid the shape of these hypodermic cells can be seen. 
The cell is prolonged on the one hand to come into con- 
