644 P. F. LAIDLAW. 



The ganglion cells stain very darkly, and appear to be 

 bipolar; the nucleus is finely granular and rather large, and 

 there is a small black nucleolus. 



The arrangement of ganglion cells lying on the anterior 

 side of the central mass is remarkable. On either side of the 

 middle line a group of them extends forwards like a horn 

 from the main body of ganglion cells, and curves slightly 

 inwards at its anterior extremity, ending some distance from 

 the tip of the snout. The cells constituting these two horns 

 are identical in character with the other ganglion cells. 

 Numerous nerve processes run forwards from them to the 

 tip of the snout, others run down to join the groups of fibres 

 entering the brain anteriorly (fig. 1, H.). 



The tip of the proboscis then appears to have a very rich 

 nerve supply, and we may conclude that the pi'oboscis is the 

 chief seat of the tactile sense. Possibly with this is corre- 

 lated the presence on the proboscis of the papillae already 

 referred to, although such papillae are not entirely confined 

 to it. 



Organs of Reproduction. 



(a) Female. — The ovary is single, and lies at the hinder 

 end of the body nearly in the middle line ; it is short and 

 somewhat curved (fig. 1, Ov.), its length is about "12 mm., and 

 it contains from twelve to fifteen eggs, which are progressively 

 riper from behind forwards. The eggs are oblong, closely 

 pressed against each other, and have large nuclei. Their 

 protoplasm is finely granular. The nuclei have a deeply 

 staining capsule; immediately below this a number of coarse, 

 dark granules, and inside these a relatively clear space in 

 which lies a large black nucleolus (fig. 8, Ov.). As already 

 stated, the ovaiy lies in a space hollowed out in the 

 parenchyma, and is surrounded by a protoplasmic membrane 

 containing flattened nuclei. 



In front of the ovary this membrane is apparently attached 

 to a short funnel-shaped structure which ends blindly in the 



