Rev. T. Hincks on the Hydroida. 151 



these are as definite zooidal forms as the polypites themselves. 

 Thej occur on the outskirts of the colony, where they are 

 thickly distributed^ and seem to be very generally present. I 

 have lately had the opportunity, at Torquay, of reexamining 

 them, and have figured them for this paper (PL XII. figs. 7 

 and 8). They consist of an extensile filamentary body, of a 

 somewhat clavate figure at the free extremity, in which, I 

 believe, a number of thread-cells are immersed, and at the 

 base surrounded, as the polypites are, by a tubular extension 

 of thepolypary. They are in pretty constant motion, stretch- 

 ing themselves out hither and thither, and are often so much 

 attenuated as to appear like " long and slender threads of 

 gossamer." They certainly do not strike one as in any 

 respect " abnormal. '^ 



We have, then, in Podocoryne another instance amongst 

 the Hydroida of that curious polymorphism which recalls so 

 forcibly the complex structure of the Siphonophora. 



III. Note on Achaeadeia laeynx, T. S. Wright. 



Dr. Strethill Wright has given a very brief and insufficient 

 description of this species, though his figure of it is graceful 

 and characteristic. Allman has studied a young polypite, 

 obtained in Mr. Rotch's aquarium, and has embodied some 

 notes upon it in his ' Gymnoblastic Hydroids.' He conjec- 

 tures that possibly Acharadria may be only " the immature 

 state of some already described form of pennaridan Hydroid." 

 No further account of it has been published. 



I have obtained it pretty abundantly between tide-marks in 

 the island of Herm, where it was first found, I believe, by 

 Mr. Rotch. It is a well-marked and extremely beautiful 

 species. The polypites are remarkable for the freedom and 

 activity of their movements. They are able to assume a 

 drooping attitude and to sway the body over to considerable 

 distances, and so to command a wide range of the surrounding 

 water. This power is due to the peculiar constitution of the 

 polypary, the upper portion of which is composed of very 

 delicate and filmy material, and offers no resistance to the 

 motion of the polypite. A very considerable tract of the 

 polypary in the adult is thus attenuated ; and the result is a 

 freedom and variety of movement which are unknown amongst 

 other members of the tribe. 



Allman has referred to this peculiarity, though it seems not 

 to have been so strongly marked in the young polypite which 

 he examined as it is in the adult. The proboscis and the 

 capitate tentacles were also in active movement, while the 



