50 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Diego a plastic race ; the diversity of the present environments of San 

 Diego lias determined the excessive variability of that race 



Eye of Pecten irradians.* — Ida H. Hyde finds that the nerve dis- 

 tribution in this eye has been in several respects misunderstood. The 

 rods have been inadequately described ; the " retinophorse " are not the 

 visual sensory cells -whose peripheral fibres form the basal optic nerve, 

 I mi are the supporting cells of the median layer of the retina ; the 

 inner ganglionic cells do not connect with the side branch of the optic 

 nerve, but are the nerve-cells of the bipolar nerve elements ; the outer 

 ganglionic cells form a single layer, whose inner fibres are disposed in 

 a special reticular structure in the retina, and whose outer fibres make 

 direct connection with the side branch of the optic nerve ; the existence 

 of the large marginal ganglionic cells and their relations to the bipolar 

 and optic nerve were not known to other investigators of the eye of 

 Pecten ; the visual apparatus of the retina is composed of afferent and 

 efferent neurons, and the rods are true peripheral visual neurons. 



Arthropoda. 

 a. Insecta. 



Phototropism of Vanessa antiopa.f — G-. H. Parker has made an 

 interesting study of the behaviour of the mourning-cloak butterfly in 

 relation to light. In bright sunlight the insect comes to rest with the 

 head away from the source of light, when the surface on which it 

 settles is not perpendicular or very nearly perpendicular to the direction 

 of the sun's rays. Otherwise, it settles without reference to the direc- 

 tion of the rays. This negative phototropism is seen only in intense 

 sunlight and after the butterfly has been on the wing, i.e. after a 

 certain state of metabolism has been established ; for V. antiopa creeps 

 and flies toward a source of light, that is, it is positively phototropic in 

 its locomotor responses. Both negative and positive phototropism in 

 this species is independent of the " heat-rays " of sunlight. 



The position assumed in negative phototropism exposes the colour 

 patterns of the wings to fullest illumination, and probably has to do 

 with bringing the sexes together during the breeding season. 



When both eyes are painted black all phototropic responses cease 

 and the insect flies upward. Butterflies with normal eyes, liberated in 

 a perfectly dark room, come to rest near the ceiling. This upward 

 flight in both cases is due to negative geotropism, not to phototropic 

 activity. 



The butterfly remains in flight near the ground because it reacts 

 positively to large patches of bright sunlight rather than to small ones, 

 even though the latter, as in the case of the sun, may be much more 

 intense. Its retreat at night and emergence in the morning are mainly 

 due to temperature changes. 



Influence of Low Temperatures on Pupse.i — E. Krodel subjected 

 pnpa3 of Lycazna corydon and L. damon to extreme cold ( — 14° R.). 



* Mark Anniv. Vol., 1903, pp. 471-S2 (1 pi.). 



♦ Tom. cit. pp. 453-69(1 pi.). 



t Alls. Zeitschr. Entom., ix. (1004) pp. 4!)-:);"), 103-10, 134-7 (21 figs.). See 

 Zool. Zentralbl., xi. (1904) pp. 493-4. 



