SERTULARIA. 199 



few or many, — whether only one, if there be any such, or a thousand, — 

 whether it be large or small, the common source of the product is that 

 minute animal. We have seen how this creature, after an indefinite pe- 

 riod of activity, is arrested, contracts into a circular form, from which a 

 spine, with a cellular summit, arises, inhabited by a lively hydra. Like- 

 wise, it appears, how the evolution of subordinate parts is dependent on 

 the presence of internal pith, gradually diffused by their multiplication 

 and extension ; that while the specimen survives, the tendency to continual 

 increase precludes all conjecture of the dimensions to be at last attained. 

 But these are evidently influenced by age and position. 



Life once elicited in the form of the hydra, there seems an incessant 

 generation of cotemporaries and posterity, until decay or interruption of 

 the pith announces the presence of disease, or the approach of death, which 

 infallibly follows. 



Already have some prolific products been described, showing their in- 

 considerable size, though bearing a thousand animated blossoms, together 

 with their subordinate organs. But others, still smaller, and occupying 

 still more restricted bounds, sustain ten thousand, nay myriads innume- 

 rable, literally in such incredible profusion, that the free exercise of their 

 parts is prevented by their reciprocal interference. 



Such are the products I shall proceed to specify. But here the natu- 

 ralist must not be satisfied with inspecting a single specimen, though, 

 strange to say, that by multiplying the subjects of observation, he may be 

 frequently involved in perplexity. Of this an example has fallen to my 

 lot regarding the present subject : nor do I pretend to elucidate various 

 points of its history so clearly, that I can hope to satisfy the reader : for 

 in truth, they are most embarrassing. Therefore, instead of attempting to 

 reason on the identity of two products, or on their difference, according to 

 the assertion or the denial of preceding authors, I shall meantime simply 

 hold them distinct, for the purpose of advancing a few special facts, illus- 

 trating the general nature of zoophytes. 



There is no doubt that the different aspect of the two, which are de- 

 nominated Sertidaria or Nemertesia Antenuina, and Sertidaria or Nemer- 

 tesia Ramosa, as well as the detail and arrangement of the parts, is very 



