WITH the publication of the last two chapters, dealing with the 

 Echinodermata and the Enteropneusta that is of the fourth German 

 portion I bring this text-book to a close for the time being, as a 

 comparative anatomy of the Invertebrata. 



I feel that some excuse is necessary for the tardy appearance of 

 the separate parts, especially of the third (Mollusca). This was 

 mainly due to my call to the University of Zurich, where official 

 duties left only the holidays and vacations for my own work. When 

 I add that the greater number of the illustrations were drawn by 

 my own hand, the reader will, I trust, pardon the lapse of time. 

 Indeed, if he be a trained zoologist, he will be specially sympathetic 

 and indulgent, and will be able to realise my feelings as I watched 

 the fresh relays of books piling up before me at the commencement 

 of each new chapter. Original sources alone have been relied upon 

 for the subject matter of the work. 



In spite of the imperfections and deficiencies of which I am 

 only too conscious, the book appears to have been found useful, 

 judging from the favourable reception almost universally given to 

 it, and from the circumstances that, even during its appearance, 

 it was translated into foreign languages. 



I am fully aware that the matter is unequally worked up. The 

 divisions treated in the first volume are too briefly dealt with, a 

 defect which must be remedied in a new edition. Any criticisms 

 or advice with which my colleagues may favour me will be gladly 

 accepted in the spirit in which they are intended. 



I have been blamed by many for not mentioning the names of 



