PREFACE. 



IN the present Memoir there are embodied certain of the late Professor Rathke's invaluable 

 researches with rny own, so that some of the fruits of his labours now appear in an English form 

 for the first time. Whatever value may be put upon my work, of this I am confident, that we 

 have done good service to anatomy in this country by giving readers who, like myself, know only 

 their mother tongue, the advantage of some of ]Jathk.e's labours. 



Other parts of this great embryologist's works have been translated for us already by 

 Professor Huxley, and I now offer to the anatomical student more treasures from the same 

 source, which have been kindly translated for me by Mr. Power. 



With very few peers, and no superior, as an observer of facts, Professor Rathke modestly 

 limited himself in the naming of new elements ; and he really needs a continuator, who will 

 fully verify and extend his researches, without being reticent as to general and special homological 

 relations. 



Some of my own observations are accidentally mere repetitions of what that eminent 

 anatomist had noted some twenty years before, but unfamiliarity with books made them appear 

 to me to be real discoveries. 



As for myself, I have never been able to work in the same patient and uninterpreting manner 

 as Rathke was wont, for during an early period of my work I was allured out of the " old 

 paths" by Transcendentalism ; and often again since then I have found myself astray on the 

 " high priori road." 



Nevertheless, I have learned at last that if " a man will begin with certainties he shall end 

 with doubts " and to my help I liave had the frequent and friendly aid of Professor Huxley, 

 who, in this country, is most worthy to represent the great German embryologists. 



Whilst this Monograph has been passing through the press, it has undergone careful 

 revision by my talented friend Professor T. Rupert Jones. To him, to Professor Huxley, to 



a 



