1903.] | PACKARD—CLASSIFICATION OF ARTHROPODA. 159 
(ur. ¢.). The ovary (ov.) is seen to lie partly beneath but mainly 
above the intestine; the median opening of the oviduct (ovd.) 
being indicated by the arrow between the third and fourth pair of 
legs. Attention should be called to the eversible coxal sacs (c. g.), 
of which there are eleven pairs situated at the base of the legs of 
each pair; the sac is largest and most developed in the middle of 
the body and is a convoluted tube which makes three turns. The 
silk gland (s. g/.) at the end of the body is large, its direct opening 
situated at the end of the cercus, while the gland itself extends as 
far forward as the third segment from the end of the body. The 
brain and nerve-cord are large and thick, much as in Pauropus. 
The dorsal vessel, fat body, rectal glands and the salivary glands 
are not represented. 
There is in Scolopendrella a mixture of Diplopod and Thysan- 
uran characters, the former the more primitive and predominating. 
My original idea that it is a Thysanuran is certainly a mistaken 
one. The Symphyla evidently forms a group by itself, and I am 
inclined to agree with Pocock and with Kingsley that it should for 
the present be associated with Pauropods and Diplopods. Yet 
were it not for the anterior position of the genital opening we should 
regard it as the representative of a group from which the insects 
have descended. 
The Symphyla is evidently a much less primitive group than the 
Pauropoda and Diplopoda, as proved by the single genital opening 
and the Thysanuran characters it possesses. It would seem as if it 
had already begun to diverge from the Diplopod stem, and was 
becoming modified in the direction of the Thysanura.1! It is a true 
composite or prophetic type which has persisted from very early 
paleozoic times, and we may well imagine that there once existed a 
form intermediate between it and the Thysanura in which the 
genital outlet had moved back to the position it holds in Chilopods 
and insects. As I state in my Zext-Book of Entomology, *‘ cer- 
tainly Scolopendrella is the only extant Arthropod which, with the 
1 The thysanurous characters and the fact that it has but asingle pair of legs to 
a segment (unless, as Schmidt suggests, the parapodia “ represent the vestiges of 
a second pair of legs and correspond to the hinder pair of limbs of the primary 
double segment,” thus indicating I would add the diplopod origin of Scolopen- 
drella) appear to indicate that it is a form which has become considerably 
detached from the Diplopod stem, and has gone part way towards the incoming 
Thysanura. Campodea also possesses these so-called “ parapodia.” 
