ST EMMA TOIUL US. 
49 
tognatha does not give a more natural arrangement, which will 
hardly be reached until four orders of so-called Apterygogenea are 
recognized*. The recent refusal of certain eminent entomologists to 
to take this step because the groups are nearly monotypic, is, to say 
the least, unscientific, but not less so than the willingness to recognize 
as natural groups assemblages of apparently unrelated forms. Thus 
it has long been known that Machilis and Tepisma have more in com- 
mon with the Orthoptera than with Japyx, Campodea, and the Col- 
lembola, l ut each new work attempts the task of describing together 
the indiscribably diverse, with a variety of minor changes which 
go far toward rendering classification chaos. 
The Coelocheta are probably the nearest relatives of the Monocheta, 
and it is a suggestive fact that among them no six-legged larvae have 
been discovered, the youngest yet reported having 15 segments 
and the same number of legs, in a species referred by I^atzel to At- 
tractosoma. In Tysiopetalum forms with less than 30 segments are 
not yet known. It is also remarkable that the prolegs of the larva 
of Stemmatoiulus are all of the same form and size, so that it appears 
not unlikely that at the first moult nearly the full complement of 
legs for the thirty-five segments would have been added. 
In these young larvae of Stemmatoiulus the exoskeleton is still 
membranous and shrivels up on drying ; there appears to be no trace 
of the peculiar ornamentation of the surface, and the pleural sutures 
are indistinguishable. A peculiar feature is the presence on the ventral 
parts of each side of the tergites of four long bristles, of which the 
inferior is longest ; no other bristles can be made out, and it is prob- 
ably these same bristles which appear in the adult in a rudimentary 
condition. The expansion of the ventral part of the body necessary 
when the legs are added would bring the bristles more nearly into 
the subdorsal position which they occupy in the adult. The great 
size of these structures in the young larvae is another character tend- 
ing to show their primitive nature and probable homology with the 
enormous spines of geologic forms. The bristles of young Stemma- 
toiuli are, however, simple, slender, and smooth, in strong distinction 
to the barbed, clavate hair-structures of young Merocheta ; they are 
equal in length to nearly one-third of the diameter of the segments to 
which they are attached, and are directed obliquely backward, so 
that when a coiled larva is viewed from the side it appears to be sup- 
plied throughout with slender legs. 
The Colobognatha are another order presenting many primitive 
characters. No six-legged larvae are known. The youngest 
* Halida3^’s duplicate generic name for Japyx, Dicellura, would furnish an 
appropriate ordinal designation, while the name Rhabdura is proposed for an 
order to contain Campodea. 
