Royal Physical Society. 69 



and those of the circular tubes round the mouth of the um- 

 brella, are for some time after detachment, rendered opaque 

 by a layer of red granular matter, which is completely ab- 

 sorbed as the animal advances towards maturity. It is prob- 

 able that the young Cydippe undergoes several changes before it 

 arrives at maturity, but I was never able to find it again in 

 its first or more advanced stages in the waters of Morecambe 

 Bay. I had looked in vain for spermaries in several speci- 

 mens of the adult in which there were no ova. It can, indeed, 

 be scarcely said to possess even ovaries, as the eggs are not 

 amassed together in groups, but are developed separately from 

 the wall of the lateral tubes of the water-vascular system. * 



This notice on the reproduction of Cydippe is, therefore, 

 incomplete ; but I have thought it advisable to bring it before 

 the Society, as I may not have an opportunity of pursuing the 

 inquiry farther, and it possesses some importance, in so far 

 as it proves that the generative process in this class of aca- 

 lephs is very different from that which obtains in the stegan- 

 opthalmatous and gymnopthalmatous medusae. 



On the function of the tentacles. — The function of the ten- 

 tacles in Cydippe has always been a quodstio vexata amongst 

 naturalists. These magnificent appendages are generally found 

 closely packed in two large canals communicating with the 

 water-vascular system, and opening by wide apertures in the 

 lower hemisphere of the body. When the Acaleph is floating at 

 rest near the surface of the water, the tentacles are expanded, 

 and depend from beneath, like long white curling plumes, to a 

 distance of twenty times the length of the animal. Each of these 

 organs consists of a single tubular thread, fringed on one side 

 by numerous closely-set cirri, which are ranged parallel to each 

 other like the teeth of a comb or the barbs of a feather. Their 

 surfaces are crowded with minute thread cells, or stinging 

 organs, and the whole apparatus is capable of being instantly 



* Since the above was read to the Society, I have, through the kindness of 

 Mr Goodsir, received the Horw Tergestince of Will, who, in his account of the 

 reproductive system of Eucharis multicornis, an acaleph allied to Cydippe 

 describes the ovaries and spermaries as attached to opposite sides of the lateral 

 water-vascular canals. He therefore makes these animals hermaphrodite, a fact 

 which is open to doubt. 



