1903.] PACKARD—CLASSIFICATION OF ARTHROPODA. 161 
may at least be claimed that the breaking up of the Arthropoda into 
more definite, well-circumscribed groups will lead to greater exacti- 
tude and definiteness when referring to them. 
After this article was completed I discovered that A. C. Oude- 
mans as early as 1886 thus expressed his views as to the naturalness 
of the Arthropoda: ‘‘It is desirable that the group of Arthropoda 
should be given up. The groups of Acaroidea, Arachnoidea, 
Crustacea, Pantopoda, Onychophora, and Insecta are independent 
of each other, and should, therefore, be treated separately in the 
manuals. The very complicated structure would then become 
clearer to the student. A comparison of the groups with each 
can best take place afterwards and not beforehand ” (Z. ¢., p. 20). 
The following diagram will roughly indicate the different Phyla 
and the principal classes into which they are divided. It should 
be observed that the Annelidan ancestors of any of these five Phyla 
probably had few trunk-segments, being probably primitive Tro- 
chozoa with parapodia already developed. 
Insecta 
Arachnida 
Symphyla 
Crustacea 
/ | 
Merostomata / 
| Trilobita Diplopoda Chilopoda 
| 
Malacopoda 
Paasopoday = 0. TAR Sst | eee 
foot sa 
I II III IV Vv 
PALZOPODA PANCARIDA MEROPODA PROTRACHEATA ENTOMOPTERA 
Protagnostus 
(Protaspis) 
Annelida — Annelida Aumelida Annelida 
or 
Trochosphera 
PROVIDENCE, R. I., March 28, 1903. 
