VI PREFACE. 



mencecl to add to it memoirs published since 1870, 

 and have been doing so, and also adding to the earlier 

 period, at such times as I could spare from other 

 work for the last six or seven years. Sometimes Ion a,' 



a o 



intervals have elapsed during which it has had to be 

 laid aside, which circumstance, together with its having 

 been compiled in two sections, first to 1870 and then 

 to 1910, and also having had to be printed in two 

 sections, first from A to L and then from M to Z, I 

 must plead in excuse for occasional discrepancies and 

 want of uniformity in treatment. 



The authors of the ' British Tunicata ' very seldom 

 gave a date in their synonymy, nearly all the dates, 

 as will be seen on referring to that work, having had 

 to be supplied by me. To ascertain the actual year 

 of publication of the memoirs cited was often a 

 difficult matter, and indeed it was one in which I was 

 not always successful. Mistakes also have occurred 

 owing to false dates on title-pages, but some of these 

 have been detected, as in Grinelin's edition (the loth) 

 of the ' Systema Naturae ' of Linnseus, the first volume 

 of which, in seven parts, each being really a separate 

 volume, bears the date 1 788 on the title-page which 

 covers the whole of the parts. That this date applies 

 to the first part only is evident from the sixth part, 

 which contains the Tunicata, having references to 

 works more recently published, their dates however 

 not being given. It was therefore necessary to find 

 out the date of publication of the several parts, and 

 this I succeeded in doing to within a few months, 

 finding that they ranged from 1788 to 1793, the sixth 

 part having been issued early in the year 1791. An 

 account of this investigation appeared in the fourth 

 part of the ' Proceedings of the Zoological Society of 



