
No. 427.] HAIRS OF LEPIDOPTEROUS LARVAE. 565 
In Crustacea, Bethe (95) and Nusbaum (97) recognized the 
sensory neuron as a bipolar cell, the distal portion penetrating 
the hair without ramifying and the other prolongation con- 
tinuing with the nerve trunk; but, at the same time, they also 
described a plexus of cells, — not a system of neurons, but a true 
plexus. Bohumil Nemec (96) found in certain isopods a system 
of peripheral ganglia. These ganglia are centers of a hypodermal 
plexus compared by him to the plexus of Bethe. Rina Monti 
(93) described a similar plexus in insects, and Holmgren (96) 
described and figured such a network of multipolar cells with 
their processes in the larva of a sphinx moth. 
In '97 and '98 Duboscq summarized very well the results of 
many authors and added some of his own observations on 
Orthoptera and chilopods. He used both the Golgi method 
and methylen blue and discredits much of the former work on 
the nerve plexus obtained by methylen blue, and that on the 
termination of the nerves by the Golgi method. 
Sensory CELLS AND NERVES OF Bopy SENSE HAIRS. 
Following the sensory nerve trunks peripherally, they are 
seen to run straight out from the central nervous system, 
dividing dichotomously, most of the branches coming off when 
the region of the back is reached. Aftera number of divisions, 
small nerves from bipolar nerve cells join the larger trunks, 
and the peripheral parts of the larger nerves may also be traced 
to bipolar nerve cells (Fig. 5). 
In the silkworm (Bombyx mori) bipolar nerve cells are 
spindle-shaped and have a very dark nucleus, which in many 
cases nearly fills the cell body (Figs. 5-6). In most forms 
studied the cells are more nearly spherical, but yet not mark- 
edly so (Figs. 5-6). Asa general rule the sensory cell is 
quite a distance from its hair, but again in the myron sphinx 
there is a slight variation, the nerve cell being at the edge of 
the pore canal, almost in its cavity; this may not indicate 
that the nerve is really shorter, but only apparently so, because 
of the thickness of the cuticle and consequent length of the 
pore canal. 
