Miscellaneous. 309 



the principal segment of the polyp-cell. Lastly, the ventral septula 

 have still shorter and thick filaments, and the septula are continued 

 as far as the extremity of the ventral diverticula of the body-cavity. 



11. The sexual organs are seated only on the four lateral septula, 

 occur only in fully developed polyps, and in other respects are as 

 in the other Pennatulidce. 



12. The rudimentary pohjps or zooids are seated upon the dorsal 

 surface of the disk, in groups of from five to thirty or forty together. 

 Each group possesses in its interior a common cavity, and on the 

 surface as many small cavities as there are zooids ; and in each of 

 these there are eight ^ery small septa without mesenteric filaments. 

 The common cavity of each group opens by a round aperture into 

 the main cell of a polyp or into its dorsal diverticulum. 



13. Around the groups of zooids a variable number of spines are 

 often seated. It is a matter of more interest that in certain species 

 one zooid regularly possesses simple tentacles on two compartments, 

 which serve to represent the lateral ventrals ; these represent the 

 calycine tentacles of the sexually mature polypes, and are generally 

 supported by two spines. The zooid bearing these two tentacles is 

 also iisually larger than the rest. 



14. The aquiferous pore described by Fritz Miiller in the middle 

 of the frond of the RenUlce is the orifice of an isolated large zooid 

 possessing a stomach and eight septa, but no plumose tentacles, fila- 

 ments, or sexual organs, and somewhat resembling, in size and the 

 spines surrounding it, the sexually mature animal. The body- 

 cavity of this " chief zooid " opens into the end of the dorsal sinus 

 of the keel. 



15. The polyp-ceUs are lined with epithelium, muscles," and con- 

 nective tissue ; and these muscles produce the extraordinarily 

 strong extensions and contractions of which the frond of RenUJa is 

 capable. 



16. The spicxdes of the Renillce are all essentially of the same 

 form (see my ' Icones histiol.'), and, after the extraction of the calca- 

 reous salt by acids, leave a coloured organic residue of exactly the 

 form of the previous structure. — Proc. of the Phys.-med. Gesellschaft 

 in Wiirzhurg, Feb. 4, 1871. 



Observations on Urnatella, a Genus of Ciliated Polyps of the Family 

 Pedicellinidse. By Prof. Leidt. 

 This polyp is found abundantly below the dam at Fairmount, in 

 the Schuylkill River, adhering to stones and rocks, on the sides and 

 underpart not in contact with the ground. Occasionally it is 

 observed attached to the shell of the living Unio complanatus and 

 Melania virginica, and less frequently to the stem of SclioUera gra- 

 minea and the leaves of Vallisneria spiralis. In the locality named, 

 on the rocks, there may be observed, in association with Urnatella, 

 the following animals : — Spongilla fragilis, Limnias ceratophylU 

 (usually abundant and in compound bunches), Cothurnia pusilla 

 (parasitic on Urnatella and Limnias), Hydra carnea, Ag., Paludicella 



