Dr. Reid on the Development of the Medusae. 25 



semicircular plate, armed at its edge with numerous slender setae. 

 The second is shorter and has several long plumose hairs spring- 

 ing from its inferior edge, and three or four not plumose from 

 the upper surface. The terminal joint gives off at its apex four 

 stout setae, and numerous others more slender from its upper 

 edge. The first pair of jaws (fig. G) consists each of a semi- 

 circular plate furnished on its convex margin with a great num- 

 ber of long beautifully plumose filaments, and has attached to 

 one extremity two other plates, each provided with numerous 

 very slender setae on their edges. The second pair of jaws (fig. 7) 

 consists each of a semicircular plate furnished on its inner margin 

 with numerous long slender setae disposed like the teeth of a 

 comb. At one end it gives off a stout branch like a finger, 

 which is terminated by seven or eight long curved spines, and 

 at the other sends off seven or eight long stout plumose setae. 

 The organs represented at fig. 8 are perhaps the mandibles, 

 but as I did not observe their exact situation in the animal, I 

 cannot with certainty refer them to those organs. The part repre- 

 sented (fig. 9) is unique, but I do not know its nature or use. 



EXPLANATION OF PLATES VI. B. and VII. 



Plate VI. B. Fig. I. C. Mac Andrei, highly magnified. 



Fig. 2. The outer shell removed to show the animal. 



Fig. 3. Anterior antenna. 



Fig. 4. Natatory foot. 



Fig. 5. Second pair of antennas. 



Fig. 6. Oviferous foot. 



Fig. 7. Tail. 



Plate VII. Fig. 1. C. Adamsi, slightly magnified. 



Fig. 2. Anterior antenna. 



Fig. 3. Natatory foot. 



Fig. 4. Oviferous foot: a. portion highly magnified ; b. one of 

 the spines highly magnified. 



Fig. 5. Second pair of antennae. 



Fig. 6. First pair of jaws. 



Fig. 7. Second pair of jaws. 



Fig. S. Mandibles.' 



Fig. 9. ? 



III. — Observations on the Development of the Medusae. By John 

 Reid, M.D., Fellow of the Royal College of Physicians of 

 Edinburgh, and Chandos Professor of Anatomy and Medicine 

 in the University of St. Andrews*. 



[With two Plates.] 

 The following observations were made upon three colonies of the 

 larvae of a Medusa. One of these was procured on the 15th of 



* These observations were laid before the Literary and Philosophical 

 Society of St. Andrews at the Meetings of the 4th of May 1 S 46 and the 5th 

 of April 1847, and abstracts of them were printed in the ' Transactions ' of the 

 Society, and reprinted in Nos. 118 and 131 of the first series of this Journal. 



