69. 



Fig. 1?. Section of tlie anterior projection of the mantle 

 margin , 



Fig. 18. Transverse section of a palp appendage. 



Fig. 19. A pair of gill plates seen from their anterior 

 surfaces. The suspensory membrane, the "walls 

 of the plates joining the plates next in succes- 

 sion, the longitxidinal muscles, and the basis of 



I 



the chit«aous rods are shovm in sec'oion. These 

 are all cut across in separating the pair of 

 plates from the pair lying in front. (Drami from 

 a study of sections). 



Pig. 20. Portion of a gill, seen from the ventral side. 



Fig. 21. Otocvst with its canal and nerve, and a portion 

 of the cerebro-pedal commissure. A nerve fre- 

 quently leaves the commissure near to oto cystic « 

 nerve and is distributed to the muscles of the 

 foot. 



Fig. 22. Portion of the extremity of an otoo^'^stic canal, 

 showing *J»©. two closed pouches. 



Fig, 23. Inner and oxiter ends of t2ie left excretory organ 

 and genital duct, seen from the ventral side. 



Fig. 24. Two celled stage. 



