DIPLOPODA POST-EMBRYONIC DEVELOPMENT. 



!37 



of the number of segments utilised in the formation of the head) is 

 still very doubtful (p. 232), and further, in the latter, one of the 

 anterior trunk-segments, usually the second, is, as a rule, devoid of 

 extremities (Figs. 121 and 122),* so that the first three pairs of legs 

 are distributed on four segments, whereas the thorax of the Insecta, 

 as is well known, consists of three segments, each possessing a pair 

 of limbs. 



The transformation of the larva into the adult, the so-called 

 anamorphosis of the Diplopoda, has been a frequent subject of 

 investigation (Newport, Fabre, Bode, Latzel, vom Eath, and 

 others). Variations occur in different forms, but these are not of such 

 importance as to require special 

 attention from us. The most 

 important features of the post- 

 embryonic development are the 

 addition of new segments and 

 the manner in which the double 

 segment characteristic of the 

 Diplopoda originates. The for- 

 mation of new somites always 

 takes place between the anal 

 segment and that last developed 

 (Latzel), and the formation of 

 double segments is now proved 

 to be due to the fusion of two 

 of the originally distinct primi- 

 tive segments (Heathcote). 



As already mentioned, the six- 

 limbed larva has several other pairs 

 of legs as rudiments beneath the 

 integument. The number of these 

 varies in different forms. The larva 

 of Glomeris when hatched, behind 

 the three anterior well - developed 

 pairs of legs, has five more pairs of 

 truncated, freely projecting limbs 

 (vom Rath). Thus the Glomeris 

 larva, which is said not to pass 

 through a pupal stage, corresponds 



in this respect to a stage of development attained by other Diplopoda only 

 after several moults. 



The first three pairs of legs in the larva of Polydesmus (Latzel, vom Rath) 



* [In Polydesmus the second trunk-segment is devoid of limbs both in the 

 larval and adult condition. — Ed.] 



Fig. 122. — Newly-hatched larva of Polydesmus 

 complanatus (after O. vom Rath, from Lang's 

 Text-book of Comp. Anot.). a, antenna ; an, 

 anus ; frj-6.,, the three pairs of legs of the 

 larva; bt, cheeks ; gch, gnathochilarium ; Ibr, 

 labrum ; sd, the stink-glands. 



