viii PREFACE. 



experience some disappointment at the relatively narrow scope of this 

 work, will, the author trusts, find on a closer acquaintance with it, sufficient 

 compensation in the vastly extended assemblage of forms here included 

 within the ranks of the true Infusoria as compared with that dealt with in 

 any pre-existing treatise. The most notable accessions in this connection 

 are undoubtedly associated with the class Flagellata, hitherto occupying in 

 our text-books a very uncertain status upon the border-land of the animal 

 and vegetable kingdoms, but which is now shown to include an infinitely 

 varied series of unquestionable animal forms. All these Flagellata, to 

 which the author has devoted special attention, are of exceedingly minute 

 size, requiring the highest magnifying powers of modern construction for 

 their correct interpretation. The majority of the Flagellate types figured 

 and described in this treatise, indeed, not only represent the outcome of 

 the most recent research, but may be regarded also as a first instalment of 

 the almost inexhaustible harvest that awaits the garnering of the industrious 

 investigator. It is hoped that this work may in this manner constitute 

 a fresh basis of departure, and supply an incentive towards the acquisition 

 of a yet truer and more comprehensive knowledge of the diversified 

 and exquisitely beautiful representatives of this, excepting to the initiated, 

 practically invisible world. 



For the general Biologist, to whom for the most part the Infusorial 

 series represents but a single scarcely noteworthy link in the grand scheme 

 of organic nature, it has been the endeavour of the author to demonstrate 

 that there yet remain in connection with this group certain side issues of 

 the highest interest and importance. Should he combine with his general 

 knowledge of the morphology and embryology of the more highly organized 

 Metazoic animals, a practical acquaintance with that remarkable order here 

 figured and described at length under the title of the Choano- Flagellata, 

 he will scarcely fail to recognize the close bond of affinity that subsists 

 between these Infusoria and the Sponges, however much the last named 

 organisms may be apparently modified in the direction of a Metazoic 

 formula. In connection, again, with the innumerable varieties of ciliated 

 embryos of the Annelida, Echinodermata, Mollusca, and other Invertebrate 

 series, there is, as indicated in the opening pages of Vol. II., ample scope 

 for speculation with respect to the by no means improbable derivation of 

 these higher organisms from Infusoria Ciliata, of which, in their embryonic 

 condition, they are indeed, in so many cases, the most remarkable possible 

 homotypes. 



Some apology is perhaps due from the author on account of the very 

 considerable interval that has elapsed since the first announcement of this 

 work and its ultimate publication, as also for the delay that has intervened 



