424 MICROSCOPIC FORMS OF ANIMAL LIFE. 



(§ 196) or even of Frogs' spawn, as to have been mistaken for 

 such. The mode in which these masses are produced closely 

 resembles that in which the masses of Mastoloia (§ 189) or of 

 Palmella (§ 194) are formed ; since they simply result from the 

 fact, that the multitude of individuals produced by a repetition 

 of the process of self-division, remain connected with each other 

 for a time by a gelatinous exudation from the surface of their 

 cell-bodies, instead of at once becoming completely isolated. 

 From a comparison of the dimensions of the individual Ophrydia, 

 each of which is about l-120th of an inch in length, with those 

 of the composite masses, some estimate may be formed of the 

 number included in the latter ; for a cubic inch would contain 

 nearly eight millions of them, if they were closely packed ; and 

 many times that number must exist in the larger masses, even 

 making allowance for the fact that the bodies of the animalcules 

 are separated from each other by their gelatinous cushion, and 

 that the masses have their central portions occupied only by 

 water. Hence we have, in such clusters, a distinct proof of the 

 extraordinary extent to which multiplication by duplicative sub- 

 division may proceed, without the interposition of any other 

 opei^ation. These animalcules, however, free themselves at times 

 from their gelatinous bed ; and have been observed to undergo 

 an " encysting process," corresponding with that of the Vorti- 

 cellinse (§ 272). It is much to be desired that Microscopic ob- 

 servers should devote themselves systematically to the continuous 

 study of even the commonest and best known forms of these 

 Animalcules; since there is not a single one, whose entire life- 

 history, from one Generative act to another, is known to us. 

 And since it cannot be even guessed at, without such knowledge, 

 what, among the many dissimilar forms that have been described 

 by Prof. Ehrenberg and others, are to be accounted as truly dis- 

 tinct species, and what are mere phases in the existence of others 

 that are perhaps very dissimilar to them in aspect, it is obvious 

 that no credit is really to be gained by the discovery of any num- 

 ber of apparently new species, which shall be at all comparable 

 with that to be acquired by the complete and satisfactory eluci- 

 dation of the life-history of any one.' 



276. As it is among Animalcules that the action of the organs 



' The recent memoirs of Prof. Stein in " Wiegmann's Archiv," and in " Siebold and 

 KolliUer's Zeitsohrift," which have been separately published in a collective form 

 " Die Infnsionsthiere," Leipsio, 1854, contain most valuable contributions to the de- 

 siderated knowledge ; as do also the memoirs of Dr. Cohn in " Siebold and Kolliker's 

 Zeitschrift." The great work of Prof. Ehrenberg, " Die Infnsionsthierchen," will always 

 remain a standard of reference, as the basis of all our higher knowledge of these or- 

 ganisms ; but its authority has been completely destroyed by the proof which has been 

 gradually accumulating, of the erroneous conceptions on which he based his descrip- 

 tions ; first, as to what are Infusory Animalcules, a very large proportion of those con- 

 sidered by him as such being undoubtedly Plants; — second, as to the organization of the 

 true Infusoria, the complex digestive apparatus, genital organs, nervous system, and 

 organs of sense, which he believed that he had discovered in them, havino" no existence 

 but in his imagination; — and, third, as to the relations of his supposed species one to 

 another, many of these being only different states of the same. 



