STIMULATIONS IN NUDIBRANCHIATE MOLLUSKS 



441 



width 8 mm. The hood 30 mm. in diameter in either way ; the 

 foot 35 mm. in length and on the average ca. 5 mm. wide. 



As in other species of this genus, the hood is fringed with rows 

 of cirrhi; in this species it is fringed with two rows, the outer of 

 which is five times larger than those of the inner row. But the 

 cirrhi of the inner row are twice the number of the outer, uniform 

 in size and arrangement. That is, there is usually one small 

 cirrhus at the base of each large, and one between. The large 





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Fig. 1 Ventral view of the hood of Melibe leonina Gould drawn from life by 

 the author. Be, body cavitj-; Dh., base of the stalk of the left dorsal tentacle; 

 F., foot; L., left lip of the mouth ;Lc., large cirrhus ;M., mouth ;<?c., small cirrhus. 



Fig. 2 Ventral view of the hood, contracted, as in the process of swallowing; 

 note the dorsal tentacles (' rhinophores') are not contracted. Drawn from life 

 by the author. Dt., dorsal tentacle (left) ; Lc, large cirrhi; F., foot; Rh., rim of 

 the hood. (Note that the anterior part of the hood is brought caudad, e.g., to 

 bring the food near to the mouth so that the lips can take hold of it; compare the 

 position of the dorsal tentacles with that in figure 1,) 



cirrhi terminate ca. 4 mm. on each side from the midventral line 

 of the caudoventral aspect of the rim of the hood. 



This species is highly sensitive to tactile stimuli. The very 

 slightest ripple on the water disturbs it. Figure 1 shows the 

 position in which the hood is held in life; the large cirrhi (lc.) 

 are stretched outward and the small cirrhi {sc.) inward. When 

 a glass rod is introduced into the water, even with the utmost 

 care, and at ca. 20 cm. away from the animal, the hood con- 



