590 CLASS III. MYRIAPODA. 



These must be looked upon as being due to two precocious 

 ecdyses. In some cases the embryo remains within the embry- 

 onic cuticle for a short time after hatching (Julus, Polydesmus, 

 Strongylosoma) ,and a kind of resting pupal stage is passed through; 

 but in all, the larva, when it becomes free and active, has 

 three pairs of legs (Fig. 352) and a certain number, usually four, 

 of apodal segments behind. It thus presents a superficial 



FIG. 352. Two larval stages of Strongylosoma Guerinii (after Metschnikoff). In A the larva 

 is still surrounded by the cuticular envelope which bears the egg-tooth ; in B it has shed 

 this envelope and has entered upon its free life, at antenna, above and posterior to which 

 the egg-tooth can be seen ; 3, 4, 5 the three pairs of legs. 



resemblance to an apterous insect. The three pairs of legs are 

 attached to three of the first four body-segments, usually the 

 first, third or fourth (Fig. 353). Moreover some of the apodal 

 posterior segments possess the rudiments of legs beneath the 

 cuticle. The larval development takes place gradually (so- 

 called anamorphosis) and consists mainly in the increase in the 

 number of antennal joints, of ocelli, and of the segments and 

 appendages. The segments are added between the anal seg- 

 ment and the segment in front of this, either one double segment 

 at a time, or in groups of two, three, or even more. 



In Glomeris, the just-hatched larva has five pairs of rudiments (freely 

 projecting) of legs behind the three pairs of functional legs. In Polydesmus* 

 in which the functional legs are on the first, third and fourth (Fig. 353) 



* There is some conflict of evidence as to which is the apodal segment. 

 It appears certain (Sinclair) that in the embryo of Julus and Polydesmus 

 the first post-cephalic segment is apodal, and that the first 'pair of legs 

 shift forward in early larval life, leaving the second apodal. 



