278 
famerous symmetry, no trace of calcareous 
structure, no longitudinal muscles and no 
podia. The radial canal system is utterly un- 
like the water-vascular system of any known 
Kchinoderm and it is perfectly inconceivable 
how the fundamental, circumoral ring of a 
holothurian could disengage itself from the 
esophagus and migrate to the opposite end of 
the body. 
If Hidonia is a holothurian, it becomes 
virtually impossible to define the class, except 
in terms of the alimentary canal. Indeed if 
Eldonia is a holothurian, the Echinoderms 
themselves can be defined in no other terms, 
for Eldonia lacks every single character which 
justifies the customary view that holothurians 
are Echinoderms. It is far less of a strain 
on my credulity to believe that Hldonia, whose 
extraordinary nature I have no inclination to 
deny, is some sort of a Celenterate with a 
commensal worm inside or under the sub- 
umbrella, or even that it represents a hitherto 
unknown phylum, than to believe that it is a 
holothurian or is connected, save in the re- 
motest way, with the Echinoderms. 
As a final result of my examination of the 
evidence, I am forced to conclude that there 
is no sufficient justification for the belief in a 
Cambrian holothurian fauna. The external 
form of Lowisella and Mackenzia and the 
supposed alimentary canal of Hldonia can not 
be considered adequate basis for such a belief. 
There is no good evidence, either in Dr. Wal- 
cott’s material or elsewhere, to show that holo- 
thurians existed before the Carboniferous. 
But as wheels, which are certainly of a 
Chiridota-like form, occur in the Zechstein 
of Europe, and animals closely allied to our 
modern Holothuria are found in the Solen- 
hofen limestone, it is not improbable that the 
holothurians were differentiated about as 
early as the other classes of Echinoderms, ex- 
cepting the Pelmatozoa. Evidence however in 
support of such a probability is still conspicu- 
ous by its absence. 
Hupert LyMan Cuark 
MUSEUM OF COMPARATIVE ZOOLOGY, 
CAMBRIDGE, MASs., 
January 12, 1912 
SCIENCE 
(N.S. Vou. XXXV. No. 894 
BIOLOGY OF MIASTOR AND OLIGARCES 
Tue general availability of Miastor, at least 
for laboratory work, justifies the following 
summary account of the biology of this inter- 
esting form and the allied, possibly sometimes 
associated, Oligarces. 
Distribution—Miastor is probably world- 
wide in distribution, having been recorded 
from Europe, Australia, North and South 
America. We have found this genus ranging 
in New York from the upper austral Hudson 
valley to the transition or boreal Adirondack 
region. These peculiar larve have also been 
found in Connecticut and Indiana. 
Oligarces has been recorded only from 
Europe and North America, Albany and ad- 
jacent Nassau, N. Y., being the only American 
localities at present known. This species is 
probably widely distributed though presum- 
ably rarer or less easily detected. 
Larval Habits—The moist inner bark of 
various trees in the incipient stages of decay 
are likely places for Miastor larve. Chestnut. 
rails, ties, stumps, the moist bark of maple, 
oak, birch, beech and hickory indicate no 
closely restricted food habits. In addition to 
some of the above, European report Miastor 
larvee from elm, ash, ironwood and sugar-beet 
residue. 
We have found Oligarces only in decaying 
elm bark, possibly because the larve are not so 
readily detected in nature. 
Distinguishing Characters.—Large colonies 
of Miastor larve are easily recognized by the 
masses of more or less adherent yellowish or 
whitish larve, and especially by the occur- 
rence here and there of motionless individuals 
with poorly indicated segmentation and elon- 
gate, transparent areas, the developing em- 
bryos, or containing young so well developed 
as to be easily distinguished with a hand mag- 
nifier, even the form of the head and the fus- 
cous ocular spot being visible. The head of 
these larve, whether small or large, is flat- 
tened, triangular with diverging antenne and 
quite different from the strongly convex, 
usually fuscous head of Sciara larve. Mzastor 
larvee have transverse incisurial bands of 
