538 



LECTURE XXII. 



Structure like that in the snail (p. 561),* is a large oblong body 

 placed in the middle of the visceral mass. A long and slender vas 

 deferens, with which communicates a csecal tube, communicates with 

 the duct of a large albuminiparous gland or uterus {fig. 196, 5, y) 

 occupying the left side of the abdomen : the common canal terminates 

 by an orifice anterior to the mouth. From this orifice the exciting 

 organ (^fig. 197, 8) can be protruded. 



Of the naked Pteropods, fig. 198, shows the Clio borealis, of the 

 198 natural size: 1 from the 



ventral aspect, with the 

 cephalic lobes contracted : 

 2 and 3 the same, with 

 those lobes expanded, 

 showing the conical ce- 

 phalic appendages s, the 

 two tentacles 4 the eyes 

 o, the rudimental foot o, 

 and its posterior lobe k' ; 

 the fins a, a ; the gene- 

 rative pouch g ; and the 

 protruded intromittent 

 organ h, along the con- 

 cave side of which runs 

 the generative duct d. 4 

 shows the animal from 

 the dorsal aspect, with 

 the cephalic lobes con- 

 tracted. 5 and 6 show 

 the animal, as seen from 

 the right side with the 

 fins cut off, so as to ex- 

 pose e the long orifice of 

 the accessory generative 

 pouch ; i the proper generative pore, and t, the anus : p is the " con- 

 strictor cervicis " muscle ; o the rudimental foot. Each lateral lobe 

 of the head supports three of the retracted processes, which, when 

 fully expanded, form a radiated crown about the mouth. Each of 

 the six processes is perforated by numerous cavities, recognisable to 

 the naked eye as red points, but which consist each of a transparent 

 sheath inclosing a central body composed of a stem terminated by a 

 tuft of about twenty microscopic pedunculated discs, the total number 

 of which in the head of the Clio, Eschrieht, their discoverer f, 



* CCCXXX. t CCCXXIX. 



Clio borealis. 



