OYAYA 
206 [June 16, 
Packard.) 
phylogenic requirements of the early embryo of Hexapoda and Arachnida 
in which there are a number of embryonic primitive abdominal append - 
ages. Thus it preceded Campodea as a stem-form. 
Genealogy of the Myriopoda. The pseudo-hexapodous larval forms of 
Chilognatha, including the Pauropoda and the early germ of the Chilopoda 
(Geophilus), indicate that the many-legged adults were derived from what 
we have called a Leptus-form ancestor. Our present knowledge of the 
embryology of the Myriopoda shows that unlike the Arachnida and Hexa- 
poda the embryo is not provided with primitive, transitory legs. There 
seems then no direct proof that the Myriopoda had an origin common with 
that of insects and arachnida, from a Scolopendrella-like, and perhaps still 
earlier Peripatus-like ancestor; but from a six-legged form, which, however, 
may have been derived from some worm-like ancestor. The Leptus-form 
larva of Myriopoda, with their three pairs of cephalic appendages and six 
legs, may, then, be the genealogical equivalent of the six-legged Nauplius 
of Crustacea; which type is generally believed to have originated from 
the worms. 
A genealogical tree of the Myriopods would then be simply two 
branches, one representing the diplopod and the other the single paired 
type (Chilopoda), both originating from a Leptus-like six-footed ancestor 
(i. ¢., with three pairs of cephalic and three pairs of postcephalic append - 
ages). 
Dr. Erich Haase in his ‘‘ Beitrag zur Phylogenie und Ontogenie der 
Chilopoden’’ publishes a ‘*stammbaum der Protochilopoden.’’ He pro- 
poses a hypothetical group, Protosymphyla, from which the Symphyla, 
Thysanura and Chilopoda have originated. But, as we have seen, this view 
is based on mistaken views as to the relations of the Chilopods to the dip- 
lopod Myriopods, and of the homologies of Myriopods with insects. As we 
have seen, the Chilopods must have originated from a Chilognathous stock, 
or at least from a branch which arose from Pauropus-like forms, and the 
Thysanura, with Scolopendrella, must have arisen from a separate main 
branch, which led to the Hexapodous branch of the Arthropod genealogi- 
cal tree. 
For the reason stated, also, we should disagree with the views of Haeckel 
(Naturliche Schépfungsgeschichte, 1870, 2d edit.) that the Diplopod My- 
riopods were derived from the Chilopoda. In the English transaction 
(1876) he remarks. ‘‘ But these animals also originally developed out of a 
six-legged form of Tracheata, as is distinctly proved by the individual de- 
velopment of the millipede in the egg. Their embryos have at first only 
three pairs of legs, like genuine insects, and only at a later period do the 
posterior pairs of legs bud, one by one, from the growing rings of the hinder 
body. Of the two orders of Centipedes * * * * the round double- 
footed ones (Diplopoda), probably did not develop until a later period out 
of the older flat, single-footed ones (Chilopoda), by successive pairs of rings 
of the body uniting together. Fossil remains of the Chilopoda are first men- 
tioned in the Jura period.’? The Chilognaths, however, as shown by Daw- 
i 
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