ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
31 
a pair of jointed legs ; two pairs of wings (perhaps only dorsal lobes) ; 
a pair of antennae and a pair of eyes ; gnathites (three pairs) formed 
for biting. Body covered by a somewhat chitinous layer resting on a 
cellular one ; alimentary tract straight, with its terminal portions lined 
by chitin ; into its anterior end opened the ducts of a pair of secretory 
glands, and into its posterior portion several thread-like hollow tubes. 
Respiration effected by tracheae. The circulatory system consisted of 
a dorsal vessel, narrowed in the thoracic region, and the nervous of a 
double supra-cesopbageal ganglion, oesophageal cords, suboesophageal 
ganglion, and a segmentally placed series of ventral ganglia, joined by 
commissural bands. A fat-body at least partly occupied the body-cavity. 
Sexual organs paired, opening to the exterior by a median duct. Sexes 
distinct ; animal terrestrial. 
From the archentomon two or several trunks developed ; one trunk 
divided into two limbs, one of w T hich became the Cinura, which are only 
slightly modified from their ancestor ; the other limb would represent 
the Collembola, and send branches in various directions. The other 
main trunk or trunks develope rapidly and in different directions, and 
represent the different groups of the higher Insects. 
The Arachnida, Myriopods, and Peripatus are discussed, and the 
conclusion is come to that the first of those has no close relationships 
with the others or with the Hexapoda. The Crustacea seem to be 
separated from all except the Arachnida. 
The author offers the phylogenetic diagram reproduced on the 
preceding page. 
Experimental Researches on Locomotion of Arthropods. * — M. J. 
Demoor remarks that no observer has yet explained the theory of the 
production of the double step in Arthropods. The observation of the 
oscillations of the body and of the displacements of the centre of 
gravity has been greatly neglected. 
He finds that the mechanical hexapod system of Insects is that of the 
double tripod, with alternate movements. Each tripod is formed by the 
anterior and posterior legs of one side, and the median leg of the other* 
The anterior leg is a traction lever, the posterior pushes, the middle 
supports. Oscillations take place in the horizontal, vertical antero- 
posterior, and vertical transverse planes. The terrestrial progression of 
walking Insects is always walking, in the physiological sense of the word. 
The Arachnida are octopods ; the four middle levers, which are 
essentially supporting, form on the ground a basis of support triangular 
in form. The anterior limbs v draw, the posterior push. The first and 
last limbs of one side act simultaneously. Of the Crustacea, some 
species walk forwards, and some laterally. In the former the hexapod 
or octopod mode of locomotion is entirely similar to that of Insects or 
Arachnids. In the latter the limbs are indifferently organs of traction 
or propulsion. No anatomical differentiation nor any functional con- 
stancy characterizes the different appendages ; the mechanical system 
is octopod ; there is no regularity in the alternation of the limbs of 
either side. 
In all walking Arthropods which M. Demoor has examined the centre 
* Comptes Rendus, cxi. (1890) pp. 839-40. 
