678 NATURAL SCIENCE. Nov.. 



observed only spiders. Demoor's observations have been made on a 

 scorpion (Bnthus), in which he finds a more compHcated arrangement. 

 The second and third le^^s of one side are close together at the moment 

 when those of the other are far apart ; these four legs give, therefore, 

 a triangular base of support whose apex is alternately to the right 

 and left of the animal ; the first and fourth legs of the same side move 

 together, each alternating with its fellow, the first pair of legs, as in 

 insects, having a tractive, the hindermost pair a pushing function. 

 Demoor thinks that this arrangement should hold throughout the 

 arachnids, and tries to throw doubt on the results of Carlet, who gave 

 the regular motion of diagonal limbs as the walk of the common 

 wheel-web spider, Epeira diademata. According to Demoor, the 

 great relative size of the abdomen in the female Epeira makes it 

 an untrustworthy subject for such researches. Gaubert, how- 

 ever, has observed the same walk in spiders of the genus 

 Tegertaria, and we may consider the results of Carlet fully 

 confirmed, as far as spiders are concerned, by the photographic 

 researches of Dixon. The common house-spider, Tegenaria derhamii, 

 and a hunting spider, Tarentula pulvendenta, were observed by him, and 

 the rule of motion of limbs in diagonals holds in both. These species 

 are perfectly at home running on flat surfaces, and are certainly 

 better subjects for observation than the Epeirce which are rather 

 adapted for climbing on plants or about their own webs. The female 

 Epeira diademata can run, however, over a flat surface, and seems to 

 carry her abdomen clear of the ground. I have observed that the 

 proportionally larger, globular abdomen of the female E. quadrata is 

 at times a drag on her movements on a flat surface, and the hind legs 

 are often not raised from the ground but simply trailed along it. If 

 the walk of Bnthus as observed by Demoor is representative of what 

 occurs among scorpions generally, we must corisider their mode of 

 progression to differ from that of spiders. If all insects do not walk 

 alike, we may naturally expect to find differences among arachnids. 

 Dixon's observations show that while in the Tegenaria the wave of 

 motion travels from the hindmost to the foremost legs, it travels from 

 before backwards in the Tarentula, though in both cases there is a 

 pause between the action of the two sets of diagonal limbs. A reduc- 

 tion in the time of this pause, and an extension in the interval between 

 the motion of the first and last legs of the same set, would produce 

 such a walk as Demoor finds in Bnthus. 



Dixon noted that a spider often uses its palps as legs, but could 

 not determine at what time they move. Gaubert states that a palp 

 moves with the second leg of its side ; it follows, that is, the rule of 

 diagonals. 



For the walk of crustaceans we have only the researches of 

 Demoor. The prawn, Palcrmon serratus, generally uses six legs for 

 walking, which move in diagonal sets as among insects. Gebia 

 littoralis sometimes shows the same walk, but when wishing to emerge 



