510 



PROCEEDIXGS OF THE NATIONAL MUSEUM. 



vol.. XXVIII. 



p.. INTERNAL ^MORPHOLOGY. 



Bodt/ irall. Till' Ixxly wall is nuulc up of three layor.s (I), the out- 

 side layer of chitiii cells forniiuo- tli(» (>xoskeleton or cuticl(> (c. tig-. 16); 

 (2), the cellular "' hypoderiuis*' (h); (o), the connective tissue lamina 

 which lines the entire body wall and supports the alimentary- canal and 



Fli;. 1(1.— SEfTION CIF BohV WAl.l, (IK LkITCOPIITH EI IMS I'K(TOR.\ LIS. (,\KTER Cl-AIS.) f, rl'TICI.E OR 

 cmiTIN EXOSKKI.KTdN: C.t., CONN'ECTIVE TISSVE KXHOIlEKM: ll, CEI.I.r L.A R H Y I'l ll lER.M IS. 



other organs (c. t.). There is no continuous l)ody cavity, hut only a 

 series of lacunie. through which the colorless })lood is driven in spas- 

 modic currents. Furthermore these lacume are so situated that no 

 extensive cii'culation is anywhere possible, but there is instead a series 

 of limited circuits which interlace with one anotlier. 



ALLMP]NTARY CANAL. 



The mouth opens directly into a short, curved (esophagus, which 

 passes ])ackward between the supra and infra(esoi)hageal ganglion, 

 along th(> dorsal surface of the latter, and enters the ventral surface of 

 the stomach a little behind its anterior end. It is v(M-y nari'ow through- 

 out its entire length and is easily overlooked in both longitudinal and 

 transverse sections (oe. tig. IT). The stomach is many times the 

 width of the (esophagus, but is only a little wider than the intestine. 

 It is situated close to the ventral surface of the carapace and stretches 

 from just Ix'hind the eyes backward along the mid line at least to tlie 

 center of the thoracic area (st.). 



It is somewhat wider in front than posteriorly, and is also raised 

 awav from the ventral surface above the posterior end of the infra- 

 (psophageal ganglion. This raised end is produced into a median lobe 

 or c{i?cum, reaching forward over the (esophagus and l)etween the 

 ovaries or testes. The stomach tapers uniformly toward the posterior 

 end, where it opens directly into the intestine (i). There is a con- 

 striction at this point like the beginning of a sphincter muscle, but the 

 op(Miing can not be closed. The intestine, therefore, is a direct contimi- 

 ation of the stomach; it enlarges considerably just back of the stomach, 

 then contracts in the fourth thoracic segment, enlarges again in the 



