1894.] Schulze’s System of Descriptive Terms. 377 
his application of distans to the peripheral parts and the 
similar use of terms ending other in “an.” 
Comstock in his “ Guide to Practical Work in Entomology” 
says that dorsad, ventrad, cephlad, ete., indicate direction in 
parallel lines having infinite extension. “In other words 
these terms must be used in a way analogous to that in which 
we use right and left.” Lines which converge according to 
small explanatory wooden model kindly sent me by Prof. 
Wilder, are described by him as“ caudo-laterad” when 
directed from the head end to the sides, cephalo-mesad when 
in the opposite direction, “ dorso-latero-cephalad” when 
diverging from the caudal extremity toward the dorsum and 
side and so on. 
The plane passing through the principal and perlateral axis 
is termed by Schulze the “frontal” plane (a poor word as 
acknowledged by Schulze). This divides the ventral from the 
dorsal regions, but Schulze seems to get into trouble here and 
omits the usual list of terms for neighborhood. These must 
be dorso-frontal and dorso-frontad, very awkward terms and 
about as inconvenient as ventro-frontal or ventro-frontad, but 
dorsan, dorsad, and ventran, ventrad for the outer parts, come 
into line again without difficulty. It would appear more 
natural to designate this as the perlateral or lateral plane or 
the tergo-frontal plane. This would enable one to designate 
the neighborhood on either sides as frontal and tergal and the 
directions toward the plane as frontad and tergad, any part 
in the plane itself would then be tergo-frontans or frontens, 
ete. Tergo-frontal would not interfere with the normal use 
of these terms’ on either ‘side of it and: be also: in accord 
with dorsal, dorsad and ventral, ventrad, for the ventral and 
dorsal regions respectively, and would designate the duplex 
relation of this plane passing as it does between two distinct 
regions of the body. 
The third plane passing through the dorso-ventral and per- 
lateral axis, is the “ transversal” dividing the rostral from the 
caudal regions of the body; the parts lying in this plane are 
“transversan ” and the direction “ transversad” ; rostral, ros- 
"Ithaca, University Press, 1882, p. 9. 
