316 Proceedings of the Royal Physical Society. 
has lately met with the present species, in the Firth of Forth, 
has ascertained that it produces planuloid young direct from 
the summit of the ovarian sac. This affords another proof 
of the difB-culty of establishing a genus from the mode of 
development. 
I have met with this species occasionally, for some years 
past, on stones and the roots of Laminariae at Cullercoats 
and Tynemouth. From its minute size, it requires to be 
carefully looked for. 
Explanation of Plate XIV. 
Fig. 1. Polypary of Hydr actinia areolata on Natica Alder i, natural size. 
> Fig. 2. Hydractinia areolata, highly magnified. 
Fig. 3. A portion of the polypary of the same, highly magnified. 
Fig. 4. Medusoid of the same, highly magnified. 
Fig. 5. Atractylis arenosa, natural size. 
Fig. 6. The same, highly magnified. 
Fig. 7. A tentacle of the same, much enlarged. 
III. On Reproduction in ^qnoria vitrina. By T. Strethill 
Weight, M.D. Plate XV. 
In vol. i. of Agassiz's " Natural History of the United 
States/' the following passage occurs : — " As to the ^quo- 
riadee, I have no doubt that they are genuine hydroids, 
though I have not been able to trace with certainty the 
origin of the ^quoria of our coast to any true hydroid. 
But the structure of iEquoria in its adult Medusa state is 
so strictly homologous to that of all the naked-eyed Medusae, 
that even if it were ascertained that it undergoes a direct 
metamorphosis from the egg to the perfect Medusa, I would 
not hesitate to consider it as a member of the order of 
Hydroids, since it has simple radiating aquiferous tubes, a 
circular canal, and marginal tentacles closely connected with 
it, and provided with minute pigment spots at the base." 
Agassiz was doubtless correct, and he might also have pre- 
dicted that it belonged to the genus Campanularia or Lao- 
medea, as it corresponded with those genera in the presence 
of otoliths. In the beginning of this month (November) 
Mr Fulton sent me two living specimens of ^quoria vitrina, 
one about three inches in diameter, the other about six 
