MEMOIRS. 



On some Points in the Early Development of the 

 Common Newt. By W. B. Scott, B.A., Fellow of 

 the College of New Jersey, Princeton, and Henry F. 

 OsBORN, B.A., Princeton. (With Plates XX and XXI.) 



The present paper records a series of observations on 

 the development of Triton tceniatus (and partially also T. 

 cristatus), made by the writers in the Morphological 

 Laboratory of the University of Cambridge. 



It deals chiefly : (1) with the formation and character of 

 the germinal layers ; (2) the development of the notochord ; 

 (3) the extension of the body cavity into the head, and the 

 formation of mesoblastic somites in that region; (4) the 

 development of the thyroid body. 



With a view of making the following account as clear as 

 possible, we have chosen a series of embryos showing the 

 most important steps in development, and have designated 

 the stages which they represent by letters in imitation of the 

 plan adopted by Mr. Balfour in his ' Monograph on the 

 Development of the Elasmobranch Fishes.' And we have 

 further endeavoured to make these stages correspond to those 

 of Bombinator igneus, as figured by Dr. Gotte ^ in his great 

 work. As might be expected, Triton in many ways shows a 

 close resemblance to the Batrachian,^ and yet at the same 

 time it presents a number of curious and striking differences 

 from that type. In order to elucidate these we have followed 

 Dr. Gotte's arrangement as far as practicable. 



The preparation of the Triton embryos was attended with 

 considerable difficulty. It was found in all cases advisable 

 to remove the albumen from the ovum before hardening. 

 The vitellus is quite liquid, and the vitelline membrane is so 

 excessively delicate that this operation must be conducted 



* A. Gotte, ' Entwickelungsgescliicte der Unke.' 



" The term " Batracbia," is used in tliis paper iu the restricted sense as 

 equivalent to the Anurous Amphibia. 



VOL. XIX. NEW SER. G G 



