ARTHKOPODA. 25 



the branches so formed extend anteriorly and form two loops on 

 either side of the stomach ; the trunk forming the outermost of 

 the two loops in descending bifurcates again on each side. 

 There are thus three trunks on each side of the stomach, form- 

 ing an intricate plexus round the pylorus, and finally terminating 

 blindly. The long, convoluted, and much larger tubes seen on 

 each side of the digestive tract are the silk-glands; they 

 commence blindly in the posterior part of the body, and termi- 

 nate in a common duct opening on the modified ' labium ' or 

 ' spinneret.' 



On the left side of the stomach is seen a thin-walled, 

 transparent sac, the posterior end of which is connected with a 

 much-convoluted tubular gland, which bends forwards, and in 

 the preparation lies on the outer side and in advance of the sac. 

 This sac is connected anteriorly with the mouth by a wide duct. 

 The tubular gland, bladder,, and duct correspond with the 

 smaller salivary glands of the imago. 



In the intervals of the fat body fasciculi of tracheae are seen 

 diverging to distribute themselves upon the viscera. 



The following points in which the viscera of the larval form 

 differ from those of the imago may be noticed in this prepara- 

 tion : the presence of the 'fat body/ the larger calibre and lesser 

 length of the digestive canal, and the absence of convolutions, 

 and the presence and large size of the silk-glands. 



RoHeston, p. 79. 



Class ARACHNIDA. 



45. A Scorpion (Scorpio afer), to shew the exo-skeleton. 



The exo-skeleton presents a well-marked division into 

 cephalo- thoracic, abdominal, and post-abdominal regions, and 

 with the exception that the abdominal segments are here distinct 

 from each other, these divisional areas approximate closely to the 

 same parts in the lobster. The cephalo-thorax is a broad and 

 but slightly convex plate marked by a median antero-posterior 

 groove, and with a deeply emarginate anterior border. At the 

 commencement of the posterior fourth of its extent there is a 

 shallow transverse groove curving forwards on either side, 



