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XVIIL Some Ohset^ations on the Structure and Functions of tubular and cellular 

 Polypi, and of Ascidice. By Joseph Jackson IuIster, Esq. F.R.S. 



Received January 1, — Read March 6 and 13, 1834. 



JL HE more obscure functions of vitality are of such difficult investigation, and 

 possess at the same time so high an interest, that any one contributing, in however 

 small a degree, to increase our information regarding them, may hope to meet with 

 indulgence. 



This consideration encourages me to submit to the Royal Society some observations 

 made during a few weeks spent at Dover and Brighton in the autumn of 1832, and the 

 last summer. I was led to engage in them from having two years before noticed the 

 existence of currents within the tubular stem of a species of Sertularia ; and their 

 investigation has led me on to additional particulars relating to that family of zoo- 

 phytes, and other compound animals more or less resembling them, some of which 

 I am willing to hope may be new in physiology. 



The facts being only such as presented themselves during a limited stay on the coast, 

 and in part indeed requiring further observations to ascertain their true bearing, the 

 form of the original memoranda is often retained, as being probably the most satis- 

 factory. Though too circumscribed and incomplete to form a ground for new 

 arrangements or theories, they will at least show that the field from which they are 

 culled is hitherto but partially explored, and may perhaps awaken the attention of 

 inquirers more favourably circumstanced. 



Of the notices regarding tubular polypi, one on Tubularia indivisa relates princi- 

 pally to a peculiar cii'culation seen within it, and to some circumstances attending 

 its growth, absorption, and decay. Those which follow on Sertularice describe in- 

 ternal currents of a different kind, a more full observation of growth and absorption, 

 with a case of the development of ova, and some other particulars of this family. 



An account is next given of a minute Ascidia possessing a character, not I believe 

 before observed in that tribe, of distinct individuals connected by a branching stem 

 and a common circulation, and bearing in these and other points some resemblance 

 to the Sertularice, The organization and functions of this Ascidia, and of a Polyclinum 

 allied to it, are stated the more in detail, as the anatomical descriptions of' the Tu- 

 nicata by Cuvier, Savigny, and MacLeay appear to be derived almost wholly from 

 dissection. 



There are at the conclusion remarks on the natural character of some Flustrce and 

 other cellular polypi, which tend to confirm the opinion that they are of a family 



MDCCCXXXIV. 3 B 



