Dec. 1, 1S6S.] 



HARDWICKE'S SCIENCE-GOSSIP. 



275 



visitors that have wandered from other pastures. 

 Watch them : they don't mind the exudation one bit, 

 but run over and through it with perfect freedom, 

 without becoming entangled in the glairy fluid — 

 "the viscosity" — which statuaries, medallists, and 

 china-menders mix with shell-lime and albumen to 

 form their strongest cement. Why, one of these 

 jockies who was dabbed into a drop of Mr. Baker's 

 best balsam, with the feather-end of a pen, to keep 

 him still in the field of our binocular, has galloped 

 right out of it and bolted clean off the course ! They 

 will run over the surface of water ; if immersed in 

 a drop of spirit placed on the slide, they become 

 insensible and remain still, but they die in a couple 

 of minutes. 



What is the good of them ? Where do they come 

 from ? Why are they never found on anything but 

 the slug and the snail in France ? why on the slug 

 only in England ? and why are they never found on 

 either "north of Tweed," where it is said that other 

 acari are a trifle too plentiful ? I know not. Who 

 knows how the aquatic epizoa, consigned to the 

 wild waves and rushing streams, reach with unerring 

 constancy the precise species to which Nature's 

 Lawgiver has assigned them ? How is it that the 

 Achtheres of the perch and the Tracheliastes of the 

 chub, hatched and living in the same pebbly pool, 

 never interchange ? And how is it that Leniaopoda 

 and Nicothoe, born in tempestuous seas, attain un- 

 failingly the living " fleshpots " for which alone 

 they are adapted ? 



Our swift acari are said to be more numerous in 

 dry than in wet seasons, and to take more out-door 

 exercise on the slug's back when he is sick and sorry 

 than when the limacine interests are flourishing. 

 Apparently the foul-feeders, the gutter-hunters, and 

 area-sneaks, L. cinereus and L. flavus, are more 

 troubled with " company " than other species. 



Look how they pop in and out of that large 

 orifice on the right side of the back — the common 

 vestibule not only of the pulmonary air-sac, but of 

 other organs! Old Sinbad cares little for the liberties 

 they are taking : he just shows that he is aware of 

 their tricks, by giving a fidgetty twitch with the 

 marginal ring. His sensibility is of low degree. 

 Baron Eerussac, speaking on this subject, says, " I 

 have seen these terrestrial gasteropods allow their 

 skins to be eaten by others, and, in spite of large 

 wounds thus produced, show no signs of pain." 



The slugs are not strict vegetarians, like the snails : 

 the larger species are decidedly carnivorous on 

 occasions, and I regret to record a bad case of 

 downright cannibalism perpetrated by my melon- 

 stealer, who devoured, in the dark hours of the night, 

 the sole companion of his captivity, an ash-grey 

 "milk slug," L. agrestis (the devastator of the 

 farmer's root crops), nearly two inches long, leaving 

 nothing of him but the spoils of a Dahomean war- 

 rior, his head and shield. I happened afterwards 



to put under the same glass a common garden beetle 

 Carabus nemoralis, of a family hitherto considered 

 well-behaved, though somewhat malodorous, who, 

 the moment he saw the gorged glutton, rushed at 

 him with the ferocity of a wild cat, and drove his 

 gaping mandibles into him, making deep indentations 

 with his head; but in vain; the soft integument 

 yielded before his butting, and slipped out of the 

 grip of his ugly " nippers," and he could not get a 

 hold for a bite except on the keel-like ridge, the 

 carina, on sluggie's bade, from which he tugged 

 and tore out two or three big mouthfuls, without in 

 any way discomposing the proprietor, who went on 

 browsing, in a serene and unconcerned manner, on a 

 succulent cabbage-leaf. 



Where do the acari get to after entering the ante- 

 chamber we watched them into ? Some say they 

 enter the respiratory cavity and draw their nourish- 

 ment from the juices of its vascular walls ; others 

 declare that they inhabit the intestinal canal, and, 

 only visiting daylight, much against their will, when 

 forced out with the excreta, watch anxiously for a 

 favourable opportunity to reascend ; suffice it to say 

 that competent observers have found them in abun- 

 dance in both of these locations. 



They differ materially, as we might expect, from 

 the Gamasi of the beetles : the latter have the cep- 

 halo-thorax articulated, and breathe by tracheae only ; 

 but Philodromus, though a smaller, is a nobler being, 

 having his abdomen and cephalothorax distinct but 

 unarticulated, and, possessing pulmonary sacs as 

 well as tracheae, is reckoned in the order Pulmotra- 

 chearia ; his family are known as Vagantes, and he 

 has a genus nearly all to himself. He is a good 

 " object " for a tyro to try his hand, eyes, and temper 

 upon : he is a delicate fellow to manipulate, and col- 

 lapses into a mere shred upon the slightest provoca- 

 tion. Simmer him gently in liquor potassse for 

 a couple of minutes to make him transparent, and 

 then with infinite pains and patience transfer him to 

 a drop of glycerine for examination. 



In Eig. 254 1 present the reader with a dorsal view, 

 displaying only those details that are made plain 

 with the "inch-and-a-half " object-glass, the actual 

 figure being enlarged to 180 diameters ; the limbs 

 are extended ; the mouth is seen with the approxi- 

 mate maxilla flanked on either side by a three- 

 jointed palp bearing a terminal brush of bristles. 



Eig. 255, drawn from the microscope with the 

 " quarter-inch " and B eye-piece, represents a lateral 

 view of one of the legs, all of which are similarly 

 constructed : the last joint is very minute, bearing 

 in front aud above two delicate little hooks or claws 

 and a pad so far exserted as to be in some way 

 opposable to the hooks. But the most interesting 

 point of structure observable in this curious little 

 foot is that the claws, when not needed as anchors 

 to hold on by, are thrown up into a recess hi the 

 large penultimate segment evidently intended for 



