PREFACE. IX 



between the issue of the first part in October 1880, and the concluding 

 number in June 1882. With respect to that first named, it may be stated 

 that the publication, dated November 1878,* of Stein's ' Infusionsthiere ' 

 Abth. III. Heft I, devoted to the Flagellata, occasioned an almost complete 

 recasting of the manuscript referring to this group, then ready for the press, 

 the work involved being greatly increased through the fact that the 

 diagnoses and descriptions of the species figured being reserved by Stein 

 for an as yet unpublished volume, the onus of forming diagnoses from 

 these figures for the many new forms illustrated, devolved upon the author. 

 Since, again, the publication of Part I. of this Manual in October 1880, the 

 energy of Continental investigators in this department of Biology has been 

 so marked that it became requisite, at the risk of some slight delay, to 

 make suitable provision both in the text and plates of the later numbers 

 of the treatise for the record of their discoveries. No more substantial 

 illustration of this circumstance could perhaps be afforded than by a 

 reference to Part VI., devoted chiefly to the class Tentaculifera, in which 

 it will be found that no small space is occupied by the description and 

 illustration of many new and interesting species described by Maupas so 

 recently as November 1881, the same number including the results of the 

 author's yet later personal investigation of the remarkable type Dendrosoma 

 radians. Such inconvenience therefore as subscribers may have sustained 

 in consequence of its tardier issue, they will, the author hopes, consider 

 to some extent counterbalanced by the considerable augmentation and 

 continuation literally up to date of the subject-matter of this treatise. 



Having during the progress of this work received from numerous 

 English and American sources an intimation that a few suggestions 

 respecting the apparatus and means employed by the author for the 

 effectual investigation of the more minute Flagellate Infusoria would be 

 greatly appreciated, he has much pleasure in submitting, in connection with 

 PI. LI., an illustration, with accompanying explanation, of a simple method 

 whereby, with the least expenditure of manipulative energy, the best results 

 may be readily obtained. For his first acquaintance wjth this method, as 

 also for the kind permission to make the present use of the same, the 

 author's thanks are due to Mr. E. M. Nelson, F.R.M.S., one of our 

 leading and most experienced experts in the use of the higher powers of 

 the compound microscope. 



The pleasing task yet devolves upon the author of tendering his 

 grateful acknowledgments to the officers of the libraries of the various 

 scientific societies, including more especially those of the Royal, Linnean, 

 and Zoological Societies, as also of the Royal College of Surgeons, for their 



* Not received in England till January 1879. 



