Common Cockroach. 87 



us in speaking of them as 'renaF organs. The colon, which is 

 bent upon itself, and has its external surface beaded over with 

 granulation-like pouches by the action of its muscular coats, is 

 connected with the lower end of the chylific stomach by a short 

 segment of small calibre, and of similar length to that which 

 connects the upper end of the chylific stomach with the larger 

 end of the gizzard. The colon ends in a rectum, which is divided 

 into six longitudinal areae by as many longitudinal muscular bands, 

 alternating with internally-placed lamelliform projections of the 

 inner coats of the intestine. A somewhat similar arrangement 

 has already been noted in the larva of the Goat-moth (p. 80) ; and 

 in the larvae of certain Libellulidae the supply of tracheae to the 

 ridged surface thus constituted, is so abundant as to convert it 

 into a respiratory organ. On either side of the junction of the 

 crop to the oesophagus is seen the bilobed salivary gland. 



On the right side in this preparation is seen the salivary recep- 

 tacle, a pellucid bladder, reaching a little farther back than the 

 gland. The duct from this receptacle fuses with that of its fellow 

 of the opposite side, and into the common duct thus formed a second 

 duct, formed by the junction of the ducts of the two glands, is re- 

 ceived, so that all the four ducts find an outlet into the mouth by a 

 short common canal. 



An azygos nerve, the nerviis recurrens, from the 'ganglion impar' 

 or 'ganglion frontale^ of the stomato-gastric system, is seen passing 

 from before backwards to join a triangular ganglion placed a little 

 way in front of the middle point of the dorsal median line of the 

 crop. From this ganglion a nerve passes off on either side to the 

 posterior extremity of the crop, and may be seen to have an elon- 

 gated thickening developed upon it at the lower third of its length. 

 A third nerve, not seen in this preparation, has been described as 

 passing off from the centrally-placed triangular ganglion to the 

 salivary glands. The ganglion impar, from which the nervus re- 

 currens takes origin, is not seen in this preparation, being situated 

 anteriorly to the cerebral ganglia, with which it is connected by 

 delicate filaments joining it just internally to the large antennary 

 nerves. The paired ganglia of the stomato-gastric system are 

 situated some way posteriorly to the cerebral ganglia; and the 

 short nerve seen on either side of the nervus recurrens, just where 

 the salivary gland abuts upon the crop, is given off by the posterior 



