The means of defence possessed by these animals also differ very much in the different species of Myriapods. In the Centipedes the animals are provided with a powerful weapon in the great poison claws which lie just beneath the mouth, and which are provided with large poison glands, which supply a fluid which runs through a canal in the hard substance of the claw and passes into the wound made by the latter. The effect of this fluid is instantaneous on the small animals which form the food of the Centipedes. I have myself watched _Lithobius_ in this country creep up to a blue-bottle fly and seize it between the poison claws. One powerful nip and the blue-bottle was dead, as if struck by lightning. I have also seen them kill worms and also other _Lithobius_ in the same way. When another _Lithobius_ is wounded by the poison claws it seems to be paralysed behind the wound. The Millepedes, on the other hand, have no such offensive and defensive weapon. They rely for protection on the fluid secreted by the _stigmata repugnatoria_ (or _glandulae odoriferae_) mentioned before. This fluid has been shown to contain prussic acid, and has a very unpleasant odour. {37}[Illustration: FIG. 18.—_Polyxenus lagurus_ (From C. L. Koch, _Die Myriapoden_).] Most of the Millepedes are provided with these glands; but in the cave Myriapods mentioned before, the animals have not to contend against so many adversaries, and these glands almost disappear. Other Myriapods defend themselves by means of the long and stiff bristles with which they are provided, _e.g._ the little _Polyxenus_. This means of defence seems to have been more common among the fossil Myriapods than among those still living. Variations in the shape and size of the limbs are numerous, as might be expected in so large a class of animals. One of the most curious of such variations is found in a Centipede of the Scolopendra tribe, called _Eucorybas_, in which the last limbs are flattened out and provided with paddle-shaped lobes. The use of these is unknown, but it is probable that they are concerned in some way with the breeding habits of the animal. The habits of the Myriapods connected with their breeding are most interesting, but have been very insufficiently investigated. There is no doubt that a full inquiry into all such habits would be of great interest, and would help to answer some of the problems which are still unsolved in these forms. My own observations refer to two forms—_Julus terrestris_ among the Millepedes, and _Lithobius forficatus_ among the Centipedes. _Julus terrestris_ is one of the most common of the English Millepedes, and can be easily obtained. I kept them in large shallow glass vessels with a layer of earth at the bottom, and thus was able easily to watch the whole process. They breed in the months of May, June, and July. The female _Julus_ when about to lay her eggs sets to work to form a kind of nest or receptacle for her eggs.