68 



MYRIAPODA 



CHAP. 



The first appearance of the mouth appendages has been 

 already mentioned, and these are shown in Fig. 43, where the 



S.S. 

 NX. 



Tr.I. 



Fig. 42. G, gut ; Malp.T, Malpighian tube ; iV.C, nerve cord ; Tr.I, deep invagina* 

 tion by which the tracheae are formed ; y.s, yolk spherules still present ; L, first 

 appearance of legs ; S.S, part of mesoblast. (Heathcote, Post. Emb. Dev. of 

 Julus terrestris.) 



small stumps that later on change to jaws are shown. The 



figure shows the head .of a young Chilog- 

 nath seen from the lower side, and the 

 second .pair of stumps fuse together 

 later on and produce the broad plate 

 already mentioned as the characteristic 

 mouth appendage of the Order. 



After the animal is hatched it has 

 still, in the case of most Myriapods 



Fig. 43. Under surface of the (those which are uot hatched with all 



head of a young Julus ter- , . 



res^Ws; joro.wi, rudimentary the Segments Complete), to undergo a 



jaws; i)eM^.7M, rudimentary further development, and in particular' 

 mouth plate ; an, antennae. . -^ ^ 



the eyes are still unformed. The pro- 

 cess of development of the eye has only been followed out as yet 

 in the Chilognatha, and in only one form, Julus, and is so curious 

 that a short account may be of interest here. The develop- 

 ment of the eye begins (in Julus) on the fourth day after hatch- 

 ing, and continues until the animal is full grown. A single 



