340 



Professor Huxley 



[May 11, 



Fig. 2 (B) ). The adjacent upper ends of the foui- V's (WW) are 

 united together, while the outer ends of the right and left V's respec- 

 tively are attached to the corresponding lobes of the mantle. Hence 



Fig. 2. 



i.hr.ch: 



(A) Dissection of an Oyster from the left side. (B) Transverse section of the same 



taken along the line a. b. in A. 



D. dorsal; K ventral ; A anterior ; P. posterior side; mt. mantle; r.mt, l.mt. its 

 right and left lobes ; c. cucullus, or anterior hood ; ve. velamen or posterior hood ; 

 vb. vestibule; cl. cloaca; m. mouth ; p. palps; g. gullet; st. stomach; i. intes- 

 tine ; r. last part of the intestine ; an. vent ; Ir. liver ; pc. pericardium ; au. 

 auricle ; v. ventricle of the heart ; br. branchi^ ; gp. the four lamellae of the 

 branchi^ or gill plates, of which two make up the left branchia (l.brX and two 

 the right (r.6r.); su.br.ch. supra-branchial chamber; in.br.ch. infra-branchial 

 chamber the position of the " spat," or mass of eggs, being shown in the trans- 

 verse section ; u.g. urogenital aperture. The duct of the left reproductive gland 

 IS seen passing from it and ramifying over the stomach and intestine. In the 

 transverse section, the csca of the gland are shown forming a layer immediately 

 beneath the integument. Those of the right gland are marked r.g. ; g. position 

 ot the two principal nervous ganglia ; add. adductor muscle. 



ihe arrows m (A) indicate the course of the inflowing and outflowing currents. 



