NO. 6 ANNELIDA, ONYCHOPHORA, AND ARTHROPODA SNODGRASS 9/ 



antennal appendages are not known in the Crustacea. In the diplopod 

 Platyrrhacus ainanros, Pflugfelder (1932a) shows that a pair of 

 coelomic sacs is formed in the cephaHc lobes of the embryo in con- 



Lm 



Prtc 



Fig. 42. — Embryonic appendages and coelomic sacs of the procephalic region 

 of an insect, a chilopod, and a crustacean. 



A, head (protocephalon) and two following somites of young embryo of 

 Carausius morosus Brunner, ventral view (from Wiesmann, 1926). B, length- 

 wise section through cephalic appendages and coelomic sacs of embryo of 

 Scolopeiidra (from Heymons, 1901). C, lengthwise section through a coelomic 

 sac of the embryonic labral rudiment of Carausiiis (from Wiesmann, 1926). 



D, cross-section of same through labral coelomic sacs (from Wiesmann, 1926). 



E, cross-section through preantennular coelomic sacs of embryo of Hemimysis 

 lamornac (from Manton, 1928). F, cross-section through preantennal coelomic 

 sacs of embryo of Carausius (from Wiesmann, 1926). 



Am, amnion; Ant, lAnt, first antenna; Lm, labrum ; LmCS, labral coelomic 

 sac; Md, mandible; iMx, 2Mx, first and second maxillae; PntCS, postantennal 

 coelomic sac; Prnt, preantemia (preantennule) ; PrntCS, preantennal (pre- 

 antennulary) coelomic sac; Prtc, protocephalon (acron and first somite) ; Stom, 

 stomodaeum. 



nection with the protocerebral lobes of the brain (fig. 44 D, Per), 

 and a second pair in connection with the deutocerebral lobes (Dcr). 

 Hence, if there is any necessary homology between the cavities of 

 the cephalic mesoderm in different arthropods, the "protocerebral" 



