Royal Physical Society. 161 



3. On Gemmiparous Reproduction (multiplication) in Actinia dianthus. 

 By Thomas Wright, M.D. (Living specimens were exhibited.) 



The author stated that Actinia dianthus, the Plumose Sea Anemone 

 of Daly ell, was found on the shores of the Firth of Forth, generally on 

 rocks which were uncovered by the sea only at very low tides. Its habitat 

 was not extensive ; it is gregarious, great numbers being frequently found 

 in a very limited space. At Arran he had seen several hundreds closely 

 aggregated together, clothing the roof of a wide low cave, and hanging 

 down like so many membranous bags half filled with water. A similar 

 colony had existed on the perpendicular surface of a single large stone 

 opposite to the Baths at Seafield ; and, again, another on the under sur- 

 face of a large overhanging rock at Wardie. It had been a matter of 

 question with the author, how the young of these Actinias, if ejected 

 from the mouth, as in Actinia mesembryanthemum, troglodytes, bellis, 

 and gemmacea, were able to attach themselves to the rocks, instead of 

 falling down and being washed away by the tide. It was known that 

 Actinia mesembryanthemum,, troglodytes, and bellis, were exceedingly 

 prolific, Sir John Dalyell and Dr Cobbold having seen twenty or thirty 

 produced at a single litter from the first species, and yet the number of 

 very young Actinias found in situations where old specimens abounded 

 was very small, and certainly bore no proportion to the number generated. 

 The cave at Arran was very difficult of access, on account of its shallow- 

 ness and the floor being covered by a pool of water ; and the Actinias 

 were only to be reached by assuming a posture which could not be main- 

 tained for more than a few minutes. A number were, however, obtained, 

 which, being attached to sponges, were easily stripped from the rock, and 

 with them were associated a great number of very small specimens. Not 

 long afterwards, the author noticed a number of young surrounding a 

 large white dianthus in the Vivarium of a friend at Leith, and was told 

 that the Actinia, while moving round the tank, had left behind it small 

 white bodies, which separated themselves from the foot or sucker and 

 became young Actinias. Sir John Dalyell had described a similar mode 

 of multiplication in Actinia lacerata, and Hollard in Actinia rosea (?) 

 The former writer had observed that Actinia lacerata protruded from all 

 parts of its foot, stolons or suckers, which became detached, and pre- 

 sently put forth tentacles, and were developed into minute Actinias. 

 After reading Sir John Dalyell's account of Actinia lacerata, Dr Wright 

 was anxious to ascertain whether there might not be included in the pro- 

 longations separated from the foot, either true ova or germs, or some 

 tissue specialized for the production of young. In the hydroid zoophytes, 

 such as Hydra, Coryne, &c, the walls of the body consisted of three 

 elements or layers, — a dermal or integumental, an areolar or muscular, 

 and a mucous or intestinal layer ; and when gemmation took place in 

 these animals, it occurred by the protrusion of a simple diverticulum 



vol. i. p 



