442 Proceedings of the Eoyal Physical Society. 



as in Coryne all Pycnogon sacs, in all stages of development, 

 are not only destitute of tentacles, but are, according to 

 Professor Allman, covered by a layer of the chitinous poly- 

 pary or scleroderm. Such a mode of nidification, however, 

 could not take place in Hydractinia, the ccenosarcal tubes 

 of which are of exceedingly small calibre. Accordingly, we 

 find that the Pycnogon sacs in this zoophyte are formed, 

 not by the arrest or change in development of an immature 

 polyp, but by the degeneration of a tentacled polyp previ- 

 ously perfect. 



Perhaps I ought to mention here, that globular sacs are 

 occasionally found in place of the polyp, in Coryne glan- 

 dulosa (Daly ell). These are destitute of scleroderm, and 

 lined with a very dense brown endoderm, arranged in some- 

 what reticulated folds. As far as I observed, they were empty, 

 and, by constantly undergoing alternate processes of dilata- 

 tion and contraction, apjpeared to influence the circulation 

 of the zoophyte, It is possible that minute Pycnogons may 

 have existed in these sacs. 



VII. Report of the Committee on Marine Zoology. By George Logan, 

 Esq., W.S., Convener. (Specimens were exhibited.) 



The Committee had severa] excursions in the Firth of 

 Forth during the past season, and were occupied in trawling 

 and dredging, and also in sweep-net fishing on the shore. 

 Upon the 11th of May last, among numerous specimens of 

 Mollusca procured off Inchkeith, the following only were 

 worthy of notice ; recorded by Dr. M'Bean : — 1st, The 

 bivalve, Cardium norvegicum of Spengler, alive ; 2d, The 

 bivalve, Montacuta substriata of Montagu, also alive, on 

 Spatangus purpureus ; 3d, The univalve, Apenhais pes 

 pelicani of Linnaeus, alive, — it lived until the 10th of 

 September; 4th, The univalve, Pileopsis Hungaricus, or 

 Fools-cap limpet, — it was also alive upon Modiola modiolus, 

 and lived until the 20th of June ; and 5th, The Echinus 

 thyone papillosa, which spawned upon the 18th of June, and 

 died next day. 



Mr William S. Young recorded a specimen of the Psoitis 

 phantapus, which came up upon a baited line near Inch- 



