516 Mr. R. I. Pocock on the Morphology and 
simply, as “ male genitalia.” These terminologies, however, 
do not allow for the known structural and functional 
differences of the parts involved in the formation of the 
apparatus. This apparatus is exhibited in its simplest form 
in the Polydesmoidea, in which only the appendages of the 
anterior pair of the seventh segment are converted into 
organs which are furnished with a seminal pouch and duct 
and act as carriers of the sperm and as its transmitters 
into the genital apertures of the female. In the Iuloid, 
Spiroboloid, and Spirostreptoid Chilognatha both pairs of 
appendages and the two sterna of the seventh segment are 
modified as “ gonopods,” and combine to form an apparatus 
often of extreme complexity. But however complicated it 
be, its constituents are primarily resolvable into two parts, 
namely, the posterior appendage, bearing the seminal 
pouch and duct, and the anterior appendage, which forms 
a protective case or sheath for the former. The appendages 
bearing the seminal pouch and duct, whether they be the 
anterior or the posterior pair of the seventh segment, are 
the essential elements of the apparatus, and may be appro- 
priately called the phallopods. The accessory appendages 
constituting the sheath may similarly be called the coleo- 
pods. Amongst existing Chilognaths the simplest types of 
gonopods of the compound kind are found in the Colobo- 
gnatha, where both coleopods and phallopods are modified 
to a relatively slight extent. The phallopods are furnished 
apically with a tuft of bristles, but seem to be unprovided 
with seminal pouch and duct. It is probable that we have 
here a primitive condition in which this appendage was 
modified to hold a drop of sperm or a spermatophore—a 
purpose for which the arrow-headed bristles described by 
Brolemann in Brachycybe Lecontei and Plaiydesmus guate- 
malensis (Mém. Soc. Zool. Fr. 1900, pp. 109-113, pl. vii. 
figs. 76 & 82) seem well fitted. In any case, the physiological 
importance of these bristles is proved by the protection they 
receive from the modification as coleopods of the appendages 
in front of them. 
It may be assumed that the formation of true phallopods 
with internal seminal sacs was preceded by a stage in which 
the appendages were simply modified as holders and inserters 
of spermatophores. In that case, from a stage of develop- 
ment a little earlier than that presented by the Colobognatha 
may be derived hypothetically along imdependent lines the 
condition of things found in the three sections of Chilognatha 
to which Verhoeff has given the names Ascospermophora, 
Proterospermophora, and Opisthospermophora (Zool. Jahrb., 
