op•^o 



coe. 



pro- 1 



4n^c. 



prg. 



kiH: 



iocs 



p?y. 



7-' 



-^OW. 



met. 



iZS 



Oc 



Fig. 328 . The development of the Arachnida. A, Transverse section of a spider 

 embryo (Thendium), after Morin, showing the coelomic sacs (coe.) and the 

 formation of the heart (h.). n.r. nerve rudiment ; y. yolk with contained cells. 

 B, Sagittal section of a spider embryo, after Wallstabe. Coelomic sacs of 

 precheliceral segment (pre); pro. i, pro. 6, first and last segments of the 

 prosoma; prg. pregenital segment; op. 2, second, and op. 10, tenth segment 

 of the opisthosoma, C, Diagram of the scorpion embryo, altered from 

 Dawydoff. Coelomic sacs of precheliceral segment (pre.) ; 1-6 segments of the 

 prosoma; prg. pregenital segment; g.op. segment of genital operculum; pet. 

 segment of pectines ; /^^. segments of first three lung books ; co.d. coelomoducts 

 which never reach the exterior ; cox.gl. coxal glands ; goti. gonoducts ; g. gonad. 

 D, Embryo of the scorpion Buthus carpathicus, after Brauer. Stage showing 

 chc. the chelicerae ; pp. pedipalps, the four other appendages of the prosoma ; 

 prg. the pregenital segment and appendages; 7, appendage forming genital 

 operculum, succeeded by the appendages forming the pectines and those 

 which form the lung books ; 12, last of these ; met. metasoma. 



