COMPENDIUM. 273 



The stem of many hydraoid zoophytes is distinguished by divisions, 

 nodes, articulations, or whirls, or by portions resembling joints. All these 

 are larger or smaller, longer or shorter, more or less numerous, and gene- 

 rally very obscurely seen in the living product, on account of the pith ; 

 but sufficiently definite on its decay and disappearance. 



These apparent subdivisions are extremely irregular, and often so in- 

 distinct, that their presence might be deemed questionable. Amidst such 

 irregularity, however, they are not merely accidental indications ; whence, 

 naturalists have assumed them as their principal auxiliaries, in adjusting a 

 systematic arrangement of zoophytes. 



They are sometimes features of admirable regularity. A small speci- 

 men of one of the Campanulariae, only three lines high, bearing five or six 

 hydrse, exhibited twenty-four whirls, on the interval of the stalk separat- 

 ing two hydra?, and above thirty under the lower of the two, as prominent 

 and distinct as if fashioned by the art of a practised turner. 



The connection of the organic with the inorganic part, subsists under 

 considerable modifications. Thus, the stem of the Cori/na glandulosa, and 

 the PediceUina, as well as that of the Vorticella hemispherica, socialis, 

 and others of their interesting congenera, seems almost, if not absolutely, 

 organic. Either the hydra or the will of the product shews a common 

 influence over each, and over all the parts ; whereas the stem of the Tubu- 

 laria indivisa, though flexible from incapacity to sustain itself, unless 

 aided by the water, is under no control of the hydra. 



As the stem of all the nascent Sertularian Zoophytes, in as far as I 

 have observed, seems to be a simple diminutive tube, and as all the extre- 

 mities, however numerous, resolve either into single cylinders or cups, 

 bells, or the like, terminating these extremities, the mode whereby the com- 

 pound stem of aggregated tubuli originates, is not evident. Yet they are 

 only approximated. They do not form a solid cylinder, though on casual 

 inspection resembling one, nor are they invested, like plants, by a common 

 cortex. Farther, each of the tubuli being independent of the rest, it will 

 prove barren, or productive if the stem be cut over, and the most luxuri- 

 ant portion above removed. 



Thus, ten or twelve out of twenty or thirty tubuli, composing a 

 vol. n. 2 M 



