44 CHARLES S. TOMES. 



Of Reptiles and Batrachia, on the other hand, he says, that 

 in all cases the papilla becomes enclosed in a capsule ; that it 

 never stops short at the papillary stage ; and as a deduction 

 from this, that the teeth of all reptiles consist at least of 

 dentine and cementum, enamel being less constant in its oc- 

 currence. In his various writings abundant reference is 

 made to the open, grooves in which the papillae destined 

 for the teeth of reptiles originate. 



We are thus led to believe that in fish, batrachia, and 

 reptiles there is displayed some sort of progression towards 

 the more complete and more complex process characterising 

 the development of the organs in mammalia'; in other words, 

 that the transitional stages of the latter may be taken as 

 representing all that occurs in the former. 



But notwithstanding the a priori probability of some such 

 relation, I shall have to show that no such generalisations 

 can be drawn — at all events, not at all in the form 

 originally set forth. 



At this point I took up the investigation, and by a curious 

 concidence published my results at almost exactly the same 

 time as a German observer, Hertwig,^ whose observations 

 cover a good deal of the same ground, and whose figures 

 correspond very closely Avith my own ; but although the 

 dates of publication very nearly correspond, my paper, I 

 believe, takes priority. 



* Hertwig, ' Ueber Bau und Entwickelung 'der Placoidschuppen und der 

 Zahne der Selachier. Jenaische Zeitschrift ' (published September, 1874). 



Hertwig, " Ueber das Zahnsystem der Amphibieii und seine Bedeu- 

 tung," &c. 



' Archiv f. Mikr. Anat. Supplementlieft ' (published December, 1874). 



Chas. S. Tomes, " On the Development of the Teeth of the Newt, Frog," 

 &c., * Philos. Trans.,' 1875 (paper received July, 1874, read November, 

 1874. 



CAas. S. Tomes, " On the Development of the Teeth of Ophidia" ('Pbil. 

 Trans.,' 1875. Received October, 1874, read November, 1874.) 



CAas. S. Tomes, " On the Development of the Teeth of Fish" (received 

 March, read April, 1875). 



I have only very lately become acquainted with Hertwig's papers ; it will 

 be seen that my papers on the teeth of amphibia, &c., were in the hands 

 of the Royal Society, and the abstract published before the publication of his 

 paper ; whilst his paper on the development of the teeth of Selachia, was 

 published before my paper, which, however, included also the osseous 

 fishes. 



Whilst I am desirous of stating that my results were arrived at entirely 

 independently, and some of them published before his, I must add that he 

 has gone into some questions with much more minuteness than I had ; and 

 that although there are a good many points in his paper with which I do 

 not agree, it contains a very large amount of valuable and interesting 

 research, 



