32 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
of gravity leaves the base of support at each step, so that the general 
definition of walking applies to the locomotion of these organisms. 
There is a causal relation between the lateral walking of some Crustacea, 
and the globular form, the insertion of the limbs far from the axis, and 
the general conformation of these creatures. The physiology of move- 
ment of Crabs confirms the theoretical data, and requires a median 
insertion and a functional horizontality of the limbs. The foot of 
C'rustaceans is defective as a walking organ, owing to the articulation 
of the carpopodite with the ischiopodite ; this articulation is necessary 
for the production of the functional horizontality of the limb. The 
octopod walk of Scorpions is less perfect than hexapod progression, which 
in Insects is, from a mechanical point of view, very perfect. 
Is the Ommatidium a Hair-bearing Sense-bud?* — In answer to 
this question Prof. W. Patten states that he has come to the conclusion 
that the convex eye of Arthropods is a group of hair-bearing sense- 
buds. He finds hair-like pseudocones over the cone-cells of Belostoma, 
Tabanus and Vespa, and he considers his suspicion that the ommatidia 
are modified hair-bearing organs is fully confirmed by the fact that, in 
the young pupae of Vespa , the first corneal cuticula is actually provided 
with hair-like spines unquestionably formed by the hardening of the 
outer ends of the pseudocones. This spine-bearing cornea is soon shed, 
and a facetted one formed ; each facet, which is, in the main, the pro- 
duct of two newly formed cornea-forming cells, often contains, in its 
centre, the remnants of an ommatidial spine. If the ommatidia are 
hair-bearing sense-buds, we ought to find some resemblance between 
isolated hair-cells and retinophoras and isolated hair-cells acting as 
rudimentary ommatidia. This seems to be really the case, for the 
isolated hair-cells of Vespa are beyond all question double cells, and 
they contain a coiled canal which the author believes to be continuous 
with a nerve-tube. After the first pupal moult the larger component 
cell forms a long protoplasmic process which is finally converted into 
one of the bristles so abundant near the eyes. These double hair-cells 
resemble the retinophorse of Molluscs and Arthropods in their axial nerve- 
canals, the imperfect union of their twisted component cells, and in the 
position, size, and colour of their nuclei. Moreover, hair-cells have been 
found between the ommatidia in the convex eyes of Aphis , Vespa , and 
Belostoma, and in all cases the cells were surrounded by a layer of pig- 
ment, so that they bore a striking resemblance to very simple ommatidia, 
and probably functioned as such. 
The author does not think it necessary to assume, as is usually 
done, that the adult ancestors of animals 'with vesicular eyes had eyes 
in progressive stages of invagination. He thinks we may safely assume 
that primitive sense-organs, ganglia, &c., have been formed, phylogeneti- 
cally, by the telescoping of individual epithelial cells; this process, 
when repeated on togenetically, gives rise to invaginations, for invagina- 
tion probably occurs only in compound sense-organs, and then as an 
incidental result of the rapid inwandering of ganglion-cells, which, 
causing an enlargement of the inner surface of the sensory layer, gives 
rise to a warping of the whole organ. 
Anat. Anzeig., v. (1890) pp. 353-9 (4 figs.). 
