14 YOUNG OF DORIS. 



that a clear line rims round just within the edge, 

 caused hy a narrow space free from eggs The ova, 

 though numerous and close-set, occupy only the cen- 

 tral portions of the band (seen in section), there 

 being a considerable space of transparent jelly with- 

 out them, on each surface. The Doris was disturbed, 

 and seems to have finished prematurely, the latter 

 part of the ribbon being distorted. 



Within a day or two after this, the other two of the 

 same species laid their spawn ; it had much the same 

 appearance as the first, that of a long ribbon irregu- 

 larly bent or folded on itself ; that of the largest is 

 above f ths of an inch high, and 1 inch long. 



Early in March I observed, similarly attached to 

 the overhanging surface of a rock between tidemarks, 

 a ribbon of like appearance, but much larger ; about 

 fths of an inch high. Doubtless this was the spawn 

 of D. tuherculata : it hung down in a wet flaccid 

 manner, being left uncovered by the recess of the 

 tide. 



On the 19th of March I cut off a small piece of the 

 first ribbon of spawn (laid Feb. 22) and examined it 

 beneath the microscope. I found that the young 

 were fully formed, each enclosed in a globular egg, 

 perfectly transparent and colourless. The young 

 Doris, unlike the adult, which is a naked slug, inhabits 

 a transparent shell, formed like that of the nautilus, 

 from the mouth of which project two large fleshy cir- 

 cular disks set round with long cilia. These latter 

 organs were in constant and vigorous vibration, by 

 the motion of which each little animal revolved freely 

 in its egg-shell, incessantly turning upon its centre 



