^^6 ELEMENTARY BIOLOGY. [CHAP. 



into the supra-branchial chamber, internally to 

 the suspensory ligament of the gills. 



The cerebro-spla7ichnic 7ierve cotnmissures will be 

 found, closely applied to the ventro-internal walls 

 of the glandular segments of the above. The 

 vena cava here lies in the middle line immediately 

 below them. 



The reproductive glajid; a yellowish mass, 

 filling up all the available space in the infra- 

 branchial portion of the body-cavity. 



Dissect it away on one side to near the level of 

 the excretory orifice; there will thus be laid bare 

 the goiital duct. Insert a bristle into this and 

 open it up; it communicates with the supra- 

 branchial chamber immediately beneath and in- 

 ternal to the excretory orifice (Cf. Sect. B. d, 

 y). Follow the duct down and note the orifices 

 of the smaller ducts which open into it, and by 

 whose confluence it is formed. 



A good notion of the ramifying nature of this 

 duct may be obtained by means of injection. 



7/. Pick away the reproductive gland and note the 

 transverse muscles ; delicate tracts of tissue pass- 

 ing between the body-wall of opposite sides. 



Examination of the above section will render it 

 clear that the pallial lobes are paired, outgrowths 

 of the dorso-lateral portion of the body-wall. The 

 cavity which they bound during life, is sub- 

 divided — as the result of the confluence and 

 attachments of the gills — into infra and supra 

 branchial chambers ; the latter being partitioned 

 off" into two portions, the inner of which receives 

 the excretory and genital ducts. 



