70 MYRIAPODA 



animal leaA'es the egg with three pairs of appendages ; the first 

 have ah-eady the form of antennae, the second will form the 

 jaws,, hut have not yet taken their proper form, while the third 

 pair will fuse together and alter their shape so as to form the 

 curious plate that has already been mentioned as forming the 

 second pair of mouth appendages. Behind the mouth append- 

 ages will come the first three pairs of legs. The whole young 

 animal on leaving the egg is enveloped in two niemljranes. 

 These membranes are secreted by the outside layer of cells in 

 the same way that the shell or exoskeleton of the animal will be 

 eventually formed, and represent the first two moults of the 

 animal, which continues to moult its shell every year through- 

 out life. 



Of the Chilopoda, the second Order of Myriapods, all the 

 families leave the egg-shell with the full number of legs, with 

 the exception of the Lithobiidae, which have seven pairs of legs 

 including the poison-claws. The Schizotarsia, the third Order, 

 also have seven pairs of legs when hatched. 



The legs make their appearance not one by one but in 

 batches (in Julus ierrestris in batches of five). The addition of 

 legs and segments to the body takes place, not at the end of the 

 body, but between the end segment and the penultimate. 



This is a short sketch of the gradual development of the 

 Myriapoda from the ovum to the fully-grown animal. It is, I 

 am aware, a short and insufficient account of all the beautiful 

 processes by which the different organs take their rise, but space 

 is insufficient here, and too much detail would be out of place in 

 a work of this nature, which only aims at giving an outline 

 sketch of the group, which shall be intelligible to the general 

 reader who has not made a special study of such matters. 

 Before leaving the suljject, however, I must mention a few 

 of the points of interest which are to be learned from the 

 examination of the course of development which has been 

 sketched here. One of the greatest puzzles in the natural 

 history of the Order Ghilognatha has always been the double 

 segments, as they are called ; that is, in fact, the possession of 

 two pairs of legs to each segment, which is, as we have already 

 said, a distinguishing characteristic of the Order. As we have 

 seen, the Ghilognatha at an early stage of existence do not 

 possess this characteristic, which is only peculiar to the adult 



