052 SUMMARY OF CURRENT RESEARCHES RELATING TO 



merically arranged ; these form arches, and do not seem to give o9f 

 any tufts of tubes. The stigmata are very minute. 



The fresh somites as developed appear to be intercalated by two 

 at each moult between the antepenultimate and the penultimate sterna, 

 as in the Chilognatha and some of the Chilopoda. 



7- Arachnida. 



Auditory Hairs of Arachnida.* — F. Dahl has convinced himself 

 by experiment of the existence of a sense of hearing in these Arthropods. 

 A constantly repeated sound, produced without any manifestatipn 

 perceptible to the eyes of the animal, near a spider moving slowly 

 forwards, was followed each time by a sudden pause. Two kinds of 

 hairs placed on the legs and palj^s appear to Dahl to be instrumental 

 in receiving the sensations of sound : (a) a hair of equal thickness 

 throughout, fringed with a short fine pile towards the apex ; it is 

 implanted in a cup-shaped depression and is extremely mobile ; a 

 nerve is connected with the base ; (b) a hair set in rows and pro- 

 jecting outwards more than the ordinary protective hair. There are 

 objections to the theories according to which these hairs might 

 receive sensations of vibrations of the web or of the motions of the 

 air, but the idea that they are sensitive to waves of sound is supported 

 by direct observation, under a high magnifying power, of their vibra- 

 tion when a note was being sounded and of the cessation of the 

 movement when it stopped. The gradual transition in the length of 

 the hairs ajipears to the author to indicate adaptation to different notes, 

 especially as their regularity in those which he calls Kreuzpinnen, 

 which are decidedly fond of music, is marked ; here they are short 

 as if for perceiving high notes ; they show great regularity in Codotea 

 atropos also. From their constancy in the arrangement of the hairs 

 Dahl is able to classify the German spiders as follows : — 



1. EpeiridcB and TJieridiidce. Tibia provided with two rows of 

 auditory hairs ; metatarsus with a single hair ; tarsus with a depressive 

 but no projecting hair. 



2. Saltidce, Thomsidce, Lycosidce. Tibia, metatarsus, and tarsus all 

 with two rows of hairs. 



Among the Tubitelarian forms occur transitional stages, but most 

 belong to the second division. The hairs of the legs occur on the 

 upper side and are confined to the three terminal joints ; the palps 

 carry two irregular rows, on the penultimate joints only. The hairs 

 found by Henking on the back of Tromhidmm have the same mobility 

 as those just described, and Dahl has found them on the claw joints of 

 the palps of Chernetidce and of scorpions ; the pits found by Haller in 

 Ixodes very possibly come under the same category. 



S. Crustacea. 



Integument of Decapod Crustacea.t— A. N. Vitzou, by a study 

 of decapod crustaceans shortly after moulting, has been able to 



* Zool. Anzeig., vi. (1883) pp. 267-70 (2 figs.). 



t Arch. Zool. Expe'r. et Gen., x. (1882) pp. 451-576 (6 pis.). 



