NO. 6 ANNELIDA, ONYCHOPHORA, AND ARTHROPODA SNODGRASS 87 



Sollaud says, three transverse grooves which define the first seg- 

 mentation (D). The most anterior groove runs between the first 

 and second pairs of antennae, the next between the second antennae 

 and the mandibles, and the third behind the mandibles. The body of 

 the embryo is thus divided into an anterior prostomial head segment 



Fig. 38. — Early embryonic stages of a palaemonid crustacean, showing the 

 development of the procephaUc lobes and the antennules from the unsegmented 

 prostomial region, and the formation of four primary body somites. (From 

 Sollaud, 1923.) A, Leander squilla Linn. B-F, L. serratiis Pennant. 



A, ventral surface of egg showing germinal disk and anterior proliferation 

 of germ bands. B, early nauplius stage with first appearance of appendages. 

 C, later stage with germ bands united anteriorly. D, nauplius stage, with 

 caudal papilla (CdP) differentiated, but circle of ectodermal teloblasts (EcT) 

 yet incomplete. E, older nauplius embryo with ventral groove (cf) in caudal 

 papilla. F, metanauplius stage, with rudiments of first and second maxillae 

 formed on posterior part of nauplius body before generation of teloblastic 

 somites has begun. 



lAnt, first antenna; sAnt, second antenna; CdP, caudal papilla; EcT, ecto- 

 dermal teloblasts ; GD, germinal disk ; /, //, first two somites ; Lni, labrum ; 

 Aid, mandible; iMx, 2Mx, first and second maxillae; Pre, procephalic lobe; 

 Prst, prostomium ; Tel, telson. 



(Prst) bearing the procephalic lobes and the first antennae, a second 

 segment (/) bearing the second antennae, a third segment (//) bear- 

 ing the mandibles, and a terminal unsegmented piece (CdP), which 

 is the caudal papilla. The embryo is now in the nauplius stage. The 

 first segment, bearing the optic lobes and first antennae, Sollaud 



