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CHILOPODA. 601 



of Chilopods appear to be oviparous. Lithobius lays its eggs 

 singly and rolls them in the earth. The European species of 

 Scolopendra lay (in June and July) from 15 to 33 eggs (about 

 3 mm. in length) in the earth (3 to 8 cm. deep) and roll themselves 

 round them, protecting them from contact with the earth and 

 keeping them moist by a fluid secretion until they are hatched, 

 which takes place after some weeks. Gfeophilus also has been 

 observed to take care of its eggs in a similar manner. The egg is 

 surrounded by chorion which is probably formed in the oviduct. 

 The segmentation and formation of the layers appear to take 

 place very much as in the Diplopoda. Mesoblastic bands are 

 formed and become completely segmented into hollow somites. 

 The number of these in the head has been already described 

 (p. 320). In the body there is one pair of them for each pedi- 

 gerous segment, and two pairs in the genital region behind the 

 last pedigerous segment. The anal region (telson) and the 

 acron are without them. Each somite (except the three anterior) 

 becomes differentiated into three sections, a lateral in connexion 

 with the appendage, a ventral over the rudiment of the future 

 sternite, and a dorsal beneath the future tergite. The w r alls of 

 these parts give rise to muscles, etc., and the cavities disappear 

 except that of the dorsal section in some segments, in which it 

 persists as the reproductive gland. The latter is therefore at 

 first paired and segmented. So far as is known none of the 

 somites give rise to a nephridial section. 



The hypoblast surrounds the yolk, and gives rise to the walls 

 of the intestine, the oesophagus and rectum being formed from 

 ectoderm. The perivisceral spaces arise from the space between 

 ectoderm and endoderm which becomes lined by mesoderm. 



An embryonic cuticular membrane is formed by the ecto- 

 derm at an early stage, as in Diplopods, and is shed after hatching. 



The postembryonic development of Chilopods takes place on 

 two types. In Scutigeridae and Lithobiidae the young are 

 hatched with seven pairs of legs, and the larval development 

 consists in the formation of the remaining appendages as well as 

 in the increase in number of ocelli and antennal joints and in the 

 attainment of sexual maturity (so-called anamorphosis). In 

 Scolopendridae and Geophilidae on the other hand the young are 

 hatched with the full number of appendages (or of their rudi- 

 ments), and the larval development consists of the complete 



