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diameters of X. ramosum, but the ten taenia are very irregular in form 

 and number : generally about eleven are apparent, varying in thick- 

 ness and in arrangement ; and not in these particulars reducible to 

 to any established order : out of these eleven tentacula apparent roimd 

 the circumference, three or four, sometimes even five, are very thick, 

 the remaining six or seven are more or less slender, and generally ta- 

 pering to a point ; some are longer than others. The outer margins 

 of the thick tentacula are very irregular in form, generally indented or 

 waved ; and this thickness would seem to be formed by a membrane 

 spread over and connecting two or three of the smaller tentacula; 

 which smaller tentacula, so far as my observations extend, are not 

 branched like X. ramosum, but simple like X. furcatum. In refer- 

 ence to this remarkable species, I beg to advert to the suggestion 

 before noticed, that X. crassipes might be deemed a variety of X. ves- 

 titum ; and in opposition to which I would remark that the tentacula 

 of the two are perfectly distinct, X. vestitum having those of X. ra- 

 mosum, while those of X. crassipes are simple, like the tentacula of 

 X. furcatum. The average diameter of X. crassipes is from ,4^ to 

 •y-fiy of an inch ; I have, however, one very much larger. 



The ninth is the first of the three last species which I call Xanthi- 

 dia tubifera, two out of which have been previously so named by 

 other observers. All three species resemble each other in the cir- 

 cumstance that the tentacula have distinctly the appearance of tubes, 

 being more transparent, and, with the exception of X. crassipes, much 

 thicker than those of the other species of Xanthidia ; it therefore be- 

 came necessary to give them an additional designation, to mark the 

 specific distinction of these three Tubifera from each other. 



The first of these three Tubifera or tube-bearing Xanthidia, I call 

 Xanthidium tubiferum simplex ; or, leaving out the generic name, 

 Tubiferum simplex ; because the tubiform tentacula have a simple 

 termination, that being of a plain circular orifice, slightly curving out- 

 wards, like the end of a trumpet or hautboy, perhaps not unlike the 

 mouth of a leech when fixed, and in the act of drawing blood. This 

 I have found by far the most rare species, having discovered only two 

 or three during my researches, among thousands of the remaining 

 species. They have, as nearly as I can count, about fifteen tentacula 

 apparent, and they measure about -j-J-jy of an inch in diameter. 



These Tubifera, from their peculiar structure and substantial ap- 

 pearance, more than any of the other species, clearly prove that the 

 animalcule is spherical, and armed, in all parts of the body, with ten- 

 tacula. 



