354 



MOLLUSCA. 



ganglia at intervals along their course. The swellings are united by commissures. 

 The pallial cords have a ganglion near their origin from the cerebral, and are 

 connected with the pedal by commissures ; they unite in a supra-rectal ganglion 

 behind. In Ncomenin (Fig. 276) these cords are united for a short distance in 

 front, and sometimes they join behind. 



There are no special organs of sense. 



The blood corpuscles contain haemoglobin, which gives the blood a red colour. 

 There are no definite vessels, but there are two more or less marked sinuses a 



SI 



-Ttv 



Gpi, 



A 



Gps 



FIG. 276 Diagram of the central ner- 

 vous system of Neomcnia carinata 

 (after Wiren). Ce cerebral ganglion ; 

 SI stotnatogastric ganglia ; Tlv pedal 

 cord ; Gpi posterior ganglion on the 

 pedal cords ; Tld pallial cords ; Gps 

 supra-rectal ganglion (from Bronn). 



Fro. 277. Diagram of the renal and generative 

 organs and pericardium ; A, of Chaetoderma 

 nitidulum ; B, of Neomenia carinata (after 

 Wiren). Ps generative gland ; Pg opening of 

 generative gland into pericardium P ; Cg neph- 

 ridiuin ; Jls receptaculum seminis ; Co copu- 

 latory organ ; C cloaca ; S, D accessory glands. 



ventral between the intestine and the ventral surface, and a dorsal sinus, the 

 hinder part of which is contractile and supposed to represent the heart. These 

 presumably communicate with the perivisceral cavity, which contains blood. 

 Respiratory organs are supposed to be represented by some epithelial folds of 

 he cloacal wall. 



