44 Proceedings of the Royal Physical Society. 



the presence of ciliary motion was indicated by the vibratory 

 and onward movement of the milky fluid contained therein, 

 and it is evident that its function is to supply nutrient mate- 

 rial to the powerful muscular tissue of this rapidly swimming 

 medusa. 



As far as I know, no similar canals have been detected 

 in any of the other Gymnopthalmata. 



(2.) On Acanthobrachia inconspicua, T. S. W. (nov. gen. sp.) 



Umbrella hemispherical, laterally compressed. Peduncle 

 four-lipped, short. Lateral canals four ; Tentacles eight ; 

 six long, springing from the sides of the margin of the 

 umbrella ; two abortive, placed at each end of the mar- 

 gin of the umbrella. Otolithic sacs eight, two accom- 

 panying each of the tentacular bulbs which do not 

 spring from the lateral canals. Extremities of tentacles 

 furnished with large prehensile palpocils. 

 This Medusa, probably the reproductive phase of a Cam- 

 panularian zoophyte, was found in Gran ton Harbour in th e 

 summer of 1862. It is remarkable for the compression 

 of its umbrella, the circular marginal canal of which pre- 

 sented an oval contour. The tentacles placed at each end 

 of the oval, are very short, and attached along the border of 

 the circular canal as far as one of the neighbouring otolites, 

 as in Plate I., figs. 2 and 3 a. The long lateral tentacles, 

 which are capable of being extended to twelve times the 

 depth of the umbrella, are distinguished by the long spinous 

 soft palpocils (fig. 4) which spring from their sides, and which 

 are capable of being protruded from the ectoderm, and of 

 adhering with singular tenacity to any object or smooth 

 surface with which they come in contact, over which they 

 spread themselves out in an irregular discoid shape, so that 

 the animal can hang by its tentacles to the sides of the vessel 

 in which it is confined. I have noticed the existence of 

 similar exaggerated palpocils on the tentacles of a gymno- 

 thalmatous medusa in my paper on Goodsirea mirabilis. In 

 both Goodsirea and Acanthobrachia, they are entirely un- 

 connected with the existence of thread-cells which are ab- 

 sent on those parts of the tentacles from which the palpocils 



