MEMOIRS OF THE NATIONAL ACADEMY OP SCIENCES. 
113 
THE BRAIN OF DIPLOPOD MYRIOPODS IN GENERA!. 
(Pis. XXIV and XXY.) 
The so-called brain or supracesophageal ganglion of a normal-eyed Myriopod is, as in insects, 
composed of four pairs of ganglia, viz, the antennal or olfactory ganglia, the procerebral ganglia, 
the optic ganglia, and lastly the commissural ganglia or lobes; the last pair of lobes being by 
no means of the physiological importance of the others. 
Newport has described and figured the brain of the European Julus terrestris. In that species 
the eyes are evidently rather far apart, since the author remarks that the optic ganglion 11 is of an 
elongated, oval, and slightly conical form, from which nervous filaments radiate outwards and 
downwards in a triangular fasciculus to the cornea ( d)P In the brain of Spirobolus marginatus, 
in which the eyes are rather large and near together, the optic ganglia are rather short, and the 
nerves to the facets form a conical mass, situated immediately behind the antennal nerve and 
extending decidedly upwards, as well as outwards, the optic nerves themselves being bulbous or 
clavate towards the facets. In Newport’s figure the optic ganglia are large and about three- 
quarters as bulky as the procerebral ganglia. Newport’s description and figure of the brain of Poly- 
desmus complanatus (Plate XXVII) show that in this and probably the entire family Polydesmidse 
the optic ganglia, optic nerves, and eyes are entirely atrophied. No observations have yet been 
made on any species of Lysiopetalidse with complete eyes, the family to which Pseudotremia 
belongs, for want of good, fresh material; but it is probable that, as shown by the following 
description and figures of Pseudotremia cavernarum and Seoterpes copei, the central nervous sys¬ 
tem is in the same place as in the Julidse. 
The brain and rudimentary eyes of Pseudotremia cavernarum. — The figures we present will give 
a better idea of the relation of parts than any description we can give. By referring to the 
longitudinal sections* (PL XXV, figs. 3 and 4) through the head of Pseudotremia one will perceive 
the relations of the brain to the rest of the head. Fig. 3 represents a section through the middle 
of the head, passing through the procerebrum (pel.) and the subcesophageal ganglion and suc¬ 
ceeding nervous tract, also the mouth and oesophagus. In Fig. 4 the section passes through one 
side of the head, involving several facets of the eye, the antennal lobe, and its nerve. In eighty 
longitudinal sections of the entire head of one specimen and thirty-two of another no traces of the 
optic nerves were to be seen, the rudimentary eyes being separate from the optic ganglia. 
Transverse sections of two heads were made, one hundred and twenty-two of one and one 
hundred of the other. In none of them were any traces of the optic nerves discovered. Figs. 
6 and 7 represent transverse sections of the brain, showing the well-developed olfactory lobes and 
the commissural lobes, but the sections in front show no traces of the optic lobes. 
Of eighty horizontal sections of the head, passing from above downward, Figs. 9 and 10 repre¬ 
sent the most instructive sections of the brain. In the section represented by Fig. 9 the eye is 
cut through and the procerebrum and optic ganglion of the left side shaved; the section also 
involves the subcesophageal ganglion. Fig. 10 represents a section a little lower down, through 
four of the facets and the end of the optic ganglion. Neither in this nor the succeeding sections 
could the optic nerve be perceived, unless a few nerve fibers passing through a small mass of 
myeloid substance (“ puntzsubstantz ”) at op. n. f be regarded as the remains of an optic nerve. It 
will be observed that the elongated conical end of the optic ganglion terminates very near the 
nearest facet, the substance of the ganglion consisting of ganglion cells and very few fibers sit¬ 
uated at the apex of the conical mass. 
The relation of the optic ganglion to the rudimentary eye and the absence of the optic nerve 
may be further seen by an inspection of the section succeeding that represented by Fig. 10 (Fig. 
11). The optic ganglion ends in a point nearly in contact with the nearest facet, but, as may 
be seen by Fig. 11a, the end of the ganglion consists of a cortical layer of ganglion cells (ge.) 
pressing against the dark hypodermis (hyp.), while within is the myeloid substance (my.) with scat- 
* I am indebted to Prof. H. C. Bumpus for sections of Pseudotremia and Seoterpes, as well as of the Crustacea, 
described in this paper. 
S. Mis. 30, pt. 2—-8 
