190 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
and granular rows was marked. In other cells the fibrils wound about, 
like those figured by Flemming in the spinal ganglion-cells of Mammals. 
The arrangement of the small “ chromophilous granules ” in rows was 
found to be due to the fact that they are situated on and between the 
fibrils. In the nerve-cells of Helix the author found structures which 
undoubtedly correspond to the centrosomes and spheres commonly found 
in other cells. 
Notes on Radulae.* * * § — Mr. F. C. Baker describes a number of radulaa 
which he has studied in preparing a report on the Molluscs of the 
Chicago area. He has also made some observations on the way in which 
the radula is used. In Limnsea , Planorbis , Pleurocera , Gampeloma, &c. 
the motion of the tongue is precisely that of a cat lapping milk. Land 
snails, on the contrary, use the jaw for cutting a piece of leaf, &c., and 
the ribbon is pressed against the jaw and assists in cutting the lower 
part of the piece selected. 
Structure of Prosobranchs.j — M. Alex. Amaudrut distinguishes 
three areas of growth in the anterior region of the Prosobranch body : — 
— (a) Terminal elongation in front of the tentacles; ( b ) intercalary or 
post-tentacular elongation ; and ( c ) dorsal intercalary elongation. These 
elongations may be isolated or combined. The object of this paper is 
to show their influence on the arrangement, form, and structure of the 
anterior organs, particularly in connection with the alimentary canal. 
Arthropoda. 
a. Insecta. 
Wings of Insects.^ — MM. J. H. Comstock and J. G-. Needham discuss 
the importance of a study of the homologies of the wing- veins, and de- 
scribe their method. In this preliminary chapter they hardly advance 
beyond the sentence that “ although there is no doubt that the courses 
of the principal wing-veins of primitive insects were determined by the 
position of the principal tracheae of the wings, the wing-veins have 
been more or less modified to meet the needs of adult life ; while at 
the same time the tracheae of the immature wing, serving the purpose 
of respiration, and lying more or less free within the wing-sac, have not 
been forced to follow closely the changes in the cuticular thickenings of 
that sac.” 
Geographical Distribution of Dragon-flies. §— Mr. G. H. Carpenter 
has a learned essay on this subject. We cannot do better than quote 
from the last paragraph : — “ The largest and most dominant sub-families, 
the Libellulinae and Coenagrionidae, have the largest percentage of widely 
ranging genera. These groups, it will be remembered, are better repre- 
sented in Tertiary than in Secondary rocks, and are clearly the most 
vigorous and flourishing branches of the order. The iEschinae, a group 
which seems to have passed its zenith, and the Corduliinae, show a 
larger proportion of forms peculiar to various regions. Lastly, in the 
Gomphinae and the Agrioninaa, with an excessively large percentage of 
* Journ. Cincinnati Soc. Nat. Hist., xix. (1897) pp. 81-92 (2 pis.). 
t Comptes Rendus, cxxvi. (1898) pp. 259-62. 
X Amer. Naturalist, xxxii. (1898) pp. 43-8 (3 figs.). 
§ Proc. R. Dublin Soc., viii. (1897) pp. 439-68 (1 pi.). 
