SucUlaria.] infusorial animalcules. 217 



appends to one of his tables of fossil organisms discovered by him, the 

 following excellent remarks : — 



" I have separated the Besmidiem and Dintomaeeee, (Naviculacea), 

 from the Infusoria, and I have done so, because many distinguished 

 observers now consider these groups as decidedly belonging to the 

 vegetable kingdom. A\Tiile I believe that no accurate line of sepa- 

 ration can be di-awn between vegetables and animals, I am yet dis- 

 posed to consider the Desmidiea^ from the sum of all their characters 

 as most ueaiiy allied to the admitted vegetables, while the Biato- 

 macea, notwithstanding Thwaite's interesting observations on their 

 conjugation, still seem to me, as they have always done, to be true 

 animals. There is such apparent volition in their movements, such 

 an abundance of nitrogen in the composition of their soft parts, and 

 such resemblances between the stipitate Gomphoncmatce, and some of 

 the Vorticelldii, that I should still be disposed to class them as ani- 

 mals, even if Ehxenberg's observations of the retractile threads and 

 snail-like feet of some of the Navicxdce should not be confirmed." 



Ehrenberg, (whose skill and practice in the use of the microscope 

 has been very great,) affu'ms that all the members of the family 

 BaciUaria are decidedly animal, and characterizes them as compre- 

 hending all animalcules, distinctly or apparently polygastric, destitute 

 of alimentary canal ; the body furnished with variable undivided 

 processes, and covered by a lorica or shell. While undergoing self- 

 division they appear connected together, as it were, by a percuiTcnt 

 thread, so that they form chain-like or tabular groups. The lorica 

 of each animalcule has one or more openings, and at the places where 

 these creatures are connected together, the union is effected by means 

 of soft processes protruding thi-ough these openings. Excepting 

 Naticula, and one or two other genera, they never separate spon- 

 taneously into single individuals, but always adhere, forming polypi- 

 like concatenated masses of greater or less extent ; hence it is that 

 the term imperfect self-division has been appKed to their mode of 

 propagation. 



This family is of vast importance in. a geological point of view, 

 and the valuable obser\^ations of Professor Bailey, on the fossil forms 

 of America, are of deep interest; indeed, the laboiu^s of that eminent 



a 



